2017 births: lowest teen and young adult birth rate on record, rising rates at older ages

Highlights from the preliminary 2017 birth data

Birth rates for U.S. teens and early 20-something are at (another!) all-time low, and birth rates continue to rise at ages 40 and older.

Another important milestone is that, for the first time on record (2016), birth rates for ages 30-34 exceeded the rate for ages 25-29.

As a historical demographer, who has some experience with fertility and mortality rate trends over the past century (and the century before), and I can say with conviction that the trend toward higher birth rates at ages 30+ is not really new. Birth rates for women ages 35 and older are not higher now than ever. (They're not even higher now than they were in the 1950s and 1960s.) I would argue that, rising birth rates among those in their 30s and 40s is more a return to long-run historical norms than an aberration. (First births at older ages is a newer phenomenon, the rate at older ages is nothing new.)

The National Vital Statistics Reports, published by the U.S. Centers for Disease Control and Prevention, provide historical birth rate data by age of mother as far back as 1970. Earlier years are available, but must be compiled from a variety of other sources including the older, and often PDF-scan-only Monthly Vital Statistics Reports and the U.S. Statistical Abstract. From those sources I collected data as far back as 1920, with complete annual data from 1935-present. The historical birth rates (births per 1,000 women) are shown in the chart above.

I am happy to share the raw data upon request. Feel free to contact me for more information.

2015 hurricane season demography

The 2015 north Atlantic hurricane season has begun...

First - some new tools:
The Bureau of Labor statistics now has an online hurricane mapper tool that provides wage,employment, and establishment data for potential flood zones.
Info at:
http://www.bls.gov/cew/hurricane_zones/home.htm

Second - the demographics:
More than 83 million people in the U.S. live in states, from Texas to North Carolina, that are at high risk for hurricanes, according to the most recent estimates from the U.S. Census Bureau. Within those states, nearly 37 million people live in coastal communities at high risk of hurricanes, an area covering 179,000 square miles.

Hurricanes occasionally strike farther north, but despite hurricane Sandy's damage in 2012, such events are considerably less common than hurricanes in the southern states. Yet that does not make the damage any less catastropic. Early estimates place the damage from Hurricane Sandy at about 400,000 housing units damaged or destroyed, the majority of which were in New York (more than 300,000), New Jersey (approximately 70,000), and Connecticut (approximately 3,000).

While Sandy was more recent, and turned the lights off for more people, hurricane Katrina left more fatalities and damaged homes in her wake.

The Department of Housing and Urban Development estimates that in the summer of 2005 hurricanes Katrina, Rita, and Wilma damaged "more than one million housing units across five states." Of the damaged homes 515,000 were in Louisiana, 220,000 in Mississippi, and nearly 140,000 in Texas.

A full five years later, nearly 15 percent of the properties still had substantial visible repair needs, and 11 percent no longer contained a permanent residential structure. In other words, more than one quarter of the homes damaged in the 2005 hurricane season were either completely lost or were still in need of repair five years later.

Florida now more populous than New York

Earlier this week the US Census Bureau released the 2014 population estimates.

A few highlights:

Florida passed New York in population size.

North Carolina also passed Michigan, and North Dakota passed Alaska.

California still largest state in the US, but #2 Texas is adding 40,000-80,000 more people per year than California is. (Still, at that rate it will take nearly 150 years for Texas to overtake California).

New data: 2012 American Community Survey

New data released today from the 2012 American Community Survey (and also from Tuesday's release of the Current Population Survey) show no change in median household income, poverty rate, and health insurance coverage in the United States (nor change across the majority of states in the U.S.).

While this may seem like a bad news story, 2012 is the first year since the the beginning of The Great Recession in which income did not fall and poverty did not rise. While the trends do not yet show growth, 2012 may be the inflection point the economy has been waiting for.

One key point of note, older Americans seem to be faring better - or at least recovering from the recession quicker - than younger Americans with substantially lower overall rates of poverty (despite a bit of an increase from last year for those age 65+) and improving homeownership rates.

For a concise summary of the new data:
William Frey, of Brookings, discusses findings from the 2012 ACS on Morning Edition. (Note: I love that reporter/interviewer Steve Inskeep refers to today's data release as "Christmas for demographers.")

6 things you need to know about the new U.S. population estimates

New 2012 population estimates from the U.S. Census Bureau show (among other things):

• The Asian population grew fastest between 2011-12 (2.9 percent growth, or 530,000 people from 2011-12)
• The Hispanic population grew most (1.1 million increase, or 2.2 percent, from 2011-12)
• The White population only grew because of immigration (deaths exceeded births for the first time)
• 6 more counties are "majority minority" (brings the total to 353 of the nation's 3,143 counties)
• Maine is the oldest state, Utah is the youngest
• Thanks to record low fertility rates, there are fewer children under the age of 5 than there were last year

To crunch the numbers yourself, see the Census Bureau's estimates page.

2013 hurricane season begins

The 2013 north Atlantic hurricane season has begun...

More than 82 million people in the U.S. live in states, from Texas to North Carolina, that are at high risk for hurricanes, according to the most recent estimates from the U.S. Census Bureau. Within those states, nearly 37 million people live in coastal communities at high risk of hurricanes, an area covering 179,000 square miles. Hurricanes occasionally strike farther north, but despite hurricane Sandy's damage in 2012, such events are considerably less common than hurricanes in the southern states.


COMPARING TWO HURRICANES

Source: Huffington Post

Early estimates place the damage from Hurricane Sandy at about 400,000 housing units damaged or destroyed, the majority of which were in New York (more than 300,000), New Jersey (approximately 70,000), and Connecticut (approximately 3,000).

While Sandy was more recent, and turned the lights off for more people, hurricane Katrina left more fatalities and damaged homes in her wake.

The Department of Housing and Urban Development estimates that in the summer of 2005 hurricanes Katrina, Rita, and Wilma damaged "more than one million housing units across five states." Of the damaged homes 515,000 were in Louisiana, 220,000 in Mississippi, and nearly 140,000 in Texas.

By 2010, according to the HUD study, three quarters of the 2005 hurricane-damaged properties on "significantly affected" blocks were in good condition (at least on the outside*), but nearly 15 percent of the properties still had substantial visible repair needs, and 11 percent no longer contained a permanent residential structure. Louisiana homes, of the state affected, are most likely to still have unrepaired damage. Mississippi homes were most likely to be either repaired or entirely demolished and left vacant.
*We should note that these estimates do not include homes with mold or other water damage issues that might render the structures uninhabitable.

From a business perspective, in the year following Katrina New Orleans had about 95,000 fewer jobs, with most losses in tourism and port operations. It took nearly two years after Katrina for the number of restaurants in New Orleans to rebound to its pre-hurricane level (according to restaurant critic Tom Fitzmorris in his book Hungry Town).


HURRICANE DEMOGRAPHICS

In addition to their physical and economic damage, major hurricanes can cause huge demographic shifts.

There were an estimated 17,500,000 residents in areas affected by hurricane Sandy and 15,000,000 residents in areas affected by hurricane Katrina.

During hurricane Sandy, approximately 850,000 residents were under evacuation orders. During Katrina approximately 1.5 million people over the age of 16 left their homes in Louisiana, Mississippi, and Alabama. And while many have returned, not all have. Between 2005 and 2010 New Orleans saw its population decline by 25 percent from an estimated 455,000 before the hurricane to 344,829 as of April 1, 2010.

And while New Orleans tends to dominate the news headlines because of the broken levees, Pass Christian, MS actually has sustained a greater proportionate loss in population. Though a small town before Katrina (just under 7,000 according to 2005 Census Bureau estimates) the population had shrunk in half in the year following the hurricane, and many residents did not return. The 2010 Census count shows a resident population of only 4,613 - a sustained decline of 34 percent since the hurricane. Gulfport, MS also declined by an estimated 5,500 residents (-8 percent) between 2005 and 2010.

Less notorious, but just as significant in terms of population shift, was Hurricane Ike in Galveston, TX. Nearly 10,000 residents remained displaced two years after the hurricane. The estimated population before Ike was 57,000 but was only 47,743 at the 2010 Census. The HUD report on housing shows that one quarter of homes in Texas hurricane-affected neighborhoods still showed significant damage in 2010, in part because of the 2005 series of hurricanes and in part because of Ike.

In natural disasters traditional sources of demographic data (building permits, school enrollment records, utility hookups, drivers licenses, etc...) are either no longer available, or provide misleading information about the displaced, remaining, and returning population. Some of the most clever demographic techniques I have seen to date were hurricane-related. At the 2010 Applied Demography conference Mark VanLandingham and Janna Knight presented their techniques for reverse-estimating the post-Katrina population of New Orleans. And Nazrul Hoque, Alelhie Valencia, and Karl Eschbach presented their techniques for filling in the data gaps for post-hurricane Galveston.

Data link roundup (week of May 31, 2013)

The week's top data analysis links...
This week's theme: fertility rates matter.


16 AND NOT PREGNANT

New data from CDC shows that teen birth rates continue to fall, and are at the lowest levels on record. According to the report:

"Teen birth rates fell at least 15% for all but two states during 2007–2011—the most recent period of sustained decline; rates fell 30% or more in seven states."

Declines were sharpest among Hispanic/Latina teens.

Source: U.S. Centers for Disease Control and Prevention

WHAT A DIFFERENCE A LITTLE ASSUMPTION MAKES

New global population growth projections by Stuart Basten, Wolfgang Lutz, and Sergei Scherbov show that a minor difference in fertility rate assumptions can make a major difference in long-range global population projections.

Like 30 billion people difference by the year 2200.

Let that sink in... then read their paper.

MASS MEDIA

In their paper (mentioned above) Basten, Lutz, and Scherbov briefly mention the factors that affect family size preference and fertility behavior. One factor they don't consider: television.

Rafael Pereira, of Urban Demographics, provides a roundup of the research on links between media exposure and reproductive behavior.


BEST CHART OF THE WEEK
... because rarely is my mind blown by the data contained in a single chart. (Really, you should read the Basten, Lutz, and Scherbov paper.)

Excerpted from Basten, Lutz, and Scherbov

Data link roundup (week of May 24, 2013)

The week's top data analysis links...
This week's theme: American cities are growing again

(SUB)URBAN BLIGHT?

According to a recent report by Brookings, urban centers have shown strong post-recession job growth, while the suburbs have lagged behind.

Perhaps not surprisingly, then, this week's Brooking's report showed that poverty rates are rising fastest in the 'burbs.


THE RISE OF CITIES

New estimates from the U.S. Census Bureau show that cities are growing. All of the nation's 25 largest cities (with the exception of Detroit) grew between 2010 and 2012. The largest cities, on average, outpaced population growth for the U.S. as a whole over the past two years. New York city added the most population and even Chicago reversed a years-long decline.


THE DOWNSIDE OF HOMEOWNERSHIP?

Being a homeowner has its downsides (and not just The Money Pit variety).

David G. Blanchflower of Dartmouth and Andrew J. Oswald (University of Warwick in England) argue that higher rates of homeownership are strongly correlated with higher rates of unemployment. While that sounds plausible, since (especially since the housing bubble burst) homeownership can be a barrier to economic mobility and migration, Peter Gordon isn't convinced (but he does agree that pro-ownership public policy needs a re-think).

Growth in largest U.S. cities

Source: U.S. Census Bureau

Today the Census Bureau released the 2012 population estimates for cities.

Some highlights:

• New York city added more population than any other city in the U.S.
• Texas claims some of the fastest growing cities in the country.
• The top 10 largest cities all grew, reversing population loss trends of prior years.
• In the top 25 largest cities, only Detroit continues to lose population.
• The fastest-growing cities were all smaller cities of less than 250,000 people.*

For more information, read the Census Bureau's press release on 2012 city estimates, or download the raw data and dig into the details.

*The small city, fast growth rate phenomenon makes sense from a mathematical perspective. Smaller population denominators tend to lead to larger percent change results.

Centenarians

There are more than 50,000 centenarians in the United States, according to the 2010 Census and a report on the 100-and-older population released last month by the Census Bureau.

Other interesting facts from the report:

• More than 80 percent of centenarians are women.
• The majority live in households (about one third live in nursing homes or other group quarters).
• California has the most population age 100 and older (5,921) followed by New York (4,605), and then Florida (4,090).
• Despite Florida's reputation as a retirement destination, South Dakota and Iowa have substantially higher proportions of centenarians as a share state population (0.0295 and 0.0278, respectively compared with Florida's 0.0218).

Image from Time magazine special section on "How to live to 100 years"

Population Profile: Alabama

POPULATION GROWTH IN ALABAMA:

Population in 2010: 4,779,735
Population in 2000: 4,447,100
Growth rate 2000 to 2010: 7.5%
Sources: U.S. Census Bureau, Census 2010 and Census 2000

Place of Birth: Percent of resident population born in the state of Alabama:

Source: U.S. Census Bureau, American Community Survey 2007-2011

AGE STRUCTURE:

Median age in 2010: 37.9

Alabama Age Structure in 2010:

Source: U.S. Census Bureau, Census 2010 and author's calculations

PUBLIC HEALTH:

Birth rate: 12.4 per 1,000 population (compared with national rate 12.7)
Fertility rate: 61.8 per 1,000 women age 15-44 (compared with national rate 63.2)
Infant mortality rate: 8.28 per 1,000 live births (compared with national rate 6.39)
Sources: U.S. Centers for Disease Control and Prevention: preliminary birth data for 2011, final death data for 2009

Life expectancy: 75.2 years (compared with national 78.6)
Source: Kaiser Family Foundation state health facts 2007

Adult obesity rate in 2011: 32.0 percent
Source: U.S. Centers for Disease Control and Prevention, Behavioral Risk Factor Surveillance System

OTHER FACTS:

Only 3.4 percent of the population in Alabama is foreign-born, compared with a national average of 12.8 percent.
Source: U.S. Census Bureau, American Community Survey 2007-2011

Despite the holiday's association with New Orleans, it is Mobile, Alabama that gets credit for hosting the first Mardi Gras celebration in North America in 1703.
Sources: CNN and History Museum of Mobile

Nation's largest metros growing, but reasons vary

America's biggest metropolitan areas are growing, but for very different reasons, according to a new report from the U.S. Census Bureau.

Among metropolitan areas of 2.5 million people or larger, only Detroit lost population between July 1, 2010 and July 1, 2011. The other twenty large metro areas all saw population growth. However, drivers of growth varied widely among metropolitan areas.

Source: U.S. Census Bureau

DRIVERS OF GROWTH:

Population change occurs because of births, deaths, and migration. Births and deaths, collectively, are referred to as "natural increase."

At the state, county, and local level, migration can measured in a variety of ways, but is often estimated in terms of net international migration (those moving into, or out of, an area from abroad) and net domestic migration (those moving into, or out of, an area from another area within the same nation).

NET DOMESTIC OUT MIGRATION IN THREE LARGEST METROS:

In the nation's three largest metropolitan areas, New York, Los Angeles, and Chicago, population grew as a result of births, longer life expectancy, and international migration.

However, net domestic migration estimates show that more residents moved out of these areas to other parts of the United States than moved into these areas between 2010 and 2011.

DON'T MESS WITH TEXAS:

The largest metropolitan areas in Texas, however, showed an entirely different pattern, acting as magnets for migration from other parts of the United States.

The Dallas-Fort Worth and Houston metro areas both grew by more than 100,000 during the year with 20 percent or more of that growth coming from net domestic migration.

SUNSHINE STATE:

Miami and Tampa, Florida's largest metropolitan areas, were also net-attractors of residents from other parts of the U.S. Miami showed fairly even population growth across all categories (20,400 natural increase, 35,200 international migrants, 36,200 domestic migrants) for net population growth of more than 92,000.

While Tampa attracted more than 27,000 domestic migrants, net international migration was less than 7,000, and an aging population resulted in net natural increase of only 2,300, the lowest of all 21 large metropolitan areas in the report.

GOLDEN STATE:

As noted above, more residents moved out of the Los Angeles metro area than moved in between 2010 and 2011. However, other large metros in California fared better. As a result of net domestic in-migration San Francisco gained 5,900, Riverside-San Bernardino gained more than 15,000, and San Diego grew by 800.


Methodology and Source Notes:
The figures shown above are from the U.S. Census Bureau Population Estimates (vintage 2011). Additional information on patterns of migration can be found in the Current Population Survey report on geographic mobility.

Geography Awareness Week: Waterfront Property

This week we'll be celebrating Geography Awareness Week by highlighting unique spatial visualizations of data.

Image source and source notes: Counties are based on 2010 geography and historical populations are based on population estimates derived from decennial census data (1790-2010).
Point locations are based on population-weighted county centroids.

According to NOAA, today more than half of the U.S. population lives in a coastal county. Recent graphics from the U.S. Census Bureau put the proportion closer to one third.

Why are the two measures so different?

The answer is in how you define "coast."

The Census Bureau analysis, pictured above, defines a "coastal county" as any county in which a portion of the county's boundary is adjacent to an ocean. NOAA's analysis includes the Great Lakes in the definition of coastal. Densely populated areas, like Chicago, account for the difference in the two measurements.

Dia de los Muertos: Life expectancy trends

Historic New England cemeteries are a bit different than cemeteries in many other states in the U.S. in that they were often family plots, on local farms or homesteads, and not in a church yard.

Early Puritans rejected churchyard burials as they rebelled against other "papist" practices, as heretical and idolatrous. Instead, many 17th century New England towns set aside land as common community burial grounds. Headstone images from this period also reflect the rejection of formal Christian iconography in favor of more secular figures, such as skulls representing fate common to all men.
Source: National Park Service

As a result, a hiker often stumbles across tombstones on a typical trek in southern New England. These tiny graveyards provide a tangible record of the region's demographic history.

One of the most striking details, aside from the sizable share of persons who passed away before their fortieth birthday, was that so many tombstones were marked in years and months. In some cases, life was marked in years, months, and days.

Aged 23 years 10 months & 25 days

This is clear physical evidence of a phenomenon clearly understood by demographers: life expectancy was short at the turn of the last century.

There is, too, the startling reminder of high infant mortality in the 1900s New England. One in ten children did not survive to reach their first birthday.

Infant: age 3 months & 3 days

Pregnancy was also a dangerous condition. According to the CDC, "For every 1000 live births, six to nine women in the United States died of pregnancy-related complications." Today those trends have been sharply reversed. Across most populations infant mortality claims fewer than 7 deaths per 1,000 live births, and maternal mortality has declined to 0.1 per 1,000 life births.

But despite these dark statistics, the gravestones mark the longevity of many people who buck the trend.

Demographically speaking, life expectancy is just an average. Some people live far longer, and some much shorter. But the real life outliers are always a pleasant surprise.

Age 74 years 4 months & 20 days

Here is the life-expectancy data behind the anecdotal, archaeological evidence:

Source: U.S. Centers for Disease Control and Prevention Health Data Interactive query system, author's calculations

*Note: Data for 2010 reflect published 2009 statistics

To ensure comparable data over time, the chart above shows life expectancy for white males and for white females, at birth, from 1900 - present. Life expectancy in 1900 was lower than 50 years for whites, both men and women in the United States. Available evidence suggests that life expectancy was even shorter for minority populations (approximately 32 years of age for black men, and 33 for black women in 1900).

New paper: What counts as a house?

New applied demography research presented at the Southern Demographic Association Conference. Here is a sample...

ABSTRACT:

As a tool for fulfilling data needs for small area (subcounty) analysis, demographers are increasingly turning to administrative records such as building permits and tax assessor records as a source of data. While Census counts are considered to be the “gold standard,” administrative records provide a fine level of spatial detail and a valuable source of information for intercensal years. This analysis builds upon earlier research by comparing administrative records-based housing unit estimates developed during the 2000s decade with housing counts from the 2010 Census in San Diego County. Results show that both administrative records and Census counts have strengths and weaknesses that should be understood by the data user.

INTRODUCTION:

Increasingly sophisticated simulation modeling, used in infrastructure planning (e.g. transportation, water, sewer, energy), disaster response and emergency management, land use planning and resource conservation, requires increasing levels of detail for demographic and housing estimates.

For many years, population estimates and projections were made primarily at the national and state/provincial levels. In recent decades, they have been carried out at progressively lower levels of geography and are now routinely made for very small areas in the United States – census tracts, block groups, and traffic analysis zones. Methods are already designed for extremely small areas such as blocks and grid cells… We also note a growing demand for estimates and projections for even smaller areas such as tax assessor parcels, block faces, and street segments.
(Swanson and Pol 2005)

The housing unit method ...may hold a strong advantage in subcounty population estimates. Other techniques of small area estimation require data, such as school enrollment, auto registration, and vital events records that are often unavailable at a subcounty level, and are delayed by a year or more in cases where the data are available. Therefore the housing unit method has the advantages of both availability and timeliness as compared with other data sources.

The method consists of a very basic premise and a series of simple equations:

Population = Household Population + Group Quarters Population
where
Household Population = Occupied Housing Units x Average Household Size
where
Occupied Housing Units = Total Housing Units x Occupancy Rate

Thus, if four basic variables are known with certainty (total housing units, occupancy rate, average household size, and group quarters population) the total population of any given area can be known with certainty.

This research focuses on the housing part of the equation...

ANALYSIS:

The map, below, is part of a much larger presentation. The map shows over/under counts of housing by census tract in San Diego County, and was developed by comparing administrative records estimates to Census 2010

Full paper available upon request...

The Great Migration

The U.S. Census Bureau analyzed data on population change, by race, for two key periods that characterize The Great Migration (1910-1970) during which blacks residents moved out of the southeast.

The color of map bubbles represents the percentage point change in black population in a given city between 1910-1940 (left) and 1940-1970 (right). Darker orange shows that the black population increased as a share of the city's population. Darker blue shows that the share decreased.

Image source

What I find interesting about the 1940-1970 chart is that New Orleans and Atlanta (and, to a lesser extent, Augusta and Chattanooga) both buck the otherwise nearly universal southern trend. Each city saw an increasing proportion of black residents 1940-1970.

However, it is important to note two key caveats in the data:

• Population shares may have changed due to migration or as a result of natural increase (births, life expectancy), though most of the change is attributable to migration.
• Data are shown only for cities "that were either in the top 100 cities in the country or top 3 of a state and had a Black population of at least 100 people." This means that some change shown on the chart may have been a shift from suburbs-to-cities or vice-versa.

Teen birth rate falls to historic low

Despite the popularity of MTV’s hit show ‘16 and Pregnant’ the teen birth rate in the United States is at an all-time low.

Of the nearly 4 million babies born in the United States in 2010 (the most recent full year of data available), fewer than 375,000 were to mothers under the age of 20...

...continue reading the rest of my article on Examiner.com

Highlights:

• Highest teen birth rate in Mississippi (55 births per 1,000 women age 15-19)
• Lowest rate in New Hampshire (15.7 per 1,000)
• Pregnancy, abortion, and fetal death rate also fell, suggesting contraceptive use is to credit for the decline in births
• National rate in 2010 (17.3) is less than half the teen birth rate in 1991 (38.6) for mothers age 15-17

Data source: "Births: Final Data for 2010." August 2012. U.S. Centers for Disease Control and Prevention.

More Americans staying put

In addition to rising unemployment and declining retail sales, the recession also has more people staying put in their current residence. According to statistics from the 2010 American Community Survey, only 15 percent of Americans lived in a different home a year ago, down from more than 16 percent of the population moving in 2005. According to the Brookings Institution fewer U.S. residents moved in 2010 than in any year since 1948.*

The map shows the proportion of population that lived in a different house the prior year (data 2006-2010), with the darkest colors representing areas with the highest proportion of people who stayed in the same house, and lightest colors representing areas with the most movers. Not surprisingly, given the housing bubble, Arizona, Nevada had relatively high rates of movers, while rural areas in Louisiana, Mississippi, and Alabama had few movers.

Percent of the population who reported living in the "same house" the prior year (2008-2010).
Source: U.S. Census Bureau, American Community Survey, author's calculations

This changing migration dynamic has important repercussions for states like California, which historically were high in-migration states. Despite California's reputation as being a state of newcomers, in 2010 a majority (54 percent) of residents were California-born. (U.S. Census Bureau, Lifetime Mobility in the United States). As a result of this change, Dowell Myers asks in his article "The New Homegrown Majority in California"

"How is the stance taken by voters with regard to taxation and services different if California is growing because of migration by outsiders rather than growing from California-born residents? What does the shift from a reliance on high migration to a homegrown majority mean for today's taxpayers?"

California is not yet approaching the level of "homegrown" population seen in states like Louisiana (79 percent) or Michigan (77 percent). But neither is it like Florida, Alaska, Arizona, or Washington DC, all of which have 60 percent or more of their population born out-of-state.

*Note: Brookings puts the number of movers at 35.1 million, but I pulled the figures from the American Community Suvey for 2010 and found more than 45 million, so take the "lowest since 1948" quote with the proverbial grain of salt.

Source: U.S. Census Bureau, American Community Survey (2010),
"Selected Social Characteristics in the United States" - downloaded 12/9/11

World population = 7 billion

It just so happens that this year the United Nation's announcement that the world's population reached 7 billion coincides with the lesson I teach on demographics, population growth, and urbanization in Intro to Sociology.

In searching for materials to make this data-intensive lesson more accessible to intro students, I came across this video from National Geographic.


It provides a series of facts about global population growth in a format that is eye-catching and memorable. This video is perfect for introducing the concept of demographic change.

When good people do bad things with data - wealth and children

I used to think the "Freakonomics" folks had a good thing going. The first book was relatively well researched, and, let's face it, the book was fun to read.

However, in the past five years I have been perpetually frustrated by the authors' repeated mis-application of very basic statistical/logical priciples. Namely the authors blatantly ignore the difference between correlation and causality. If my Intro to Sociology students can pick apart the difference between correlation and causality, you would think trained economists could do the same.

The latest blunder strikes me as particularly egregious: implying that children are an "inferior good" based on oversimplified interpretation of a couple of charts. Now, whatever your take on pint-sized people may be, I suggest that a chart showing a negative correlation between GDP-per-capita and children-per-woman only shows correlation, not causality.

Even the most casual observer can see that the countries with the low income/high fertility combination are still largely agricultural or in the very early stages of industrialization. Conversely, the countries with high income/low fertility are largely industrialized or post-industrial in their development. Basic demographics teaches us that fertility is higher in agricultural societies than in industrial ones, regardless of wealth. Fertility is as much about social and cultural structure as about income.

But even more fundamental to my argument: Something really fascinating happens to those post-industrial countries... At a certain point, the fertility rate starts going back up as income increases.

Let me put this another way. Income has continued to rise in the United States from the mid-1990s to today (recession aside) and through that entire period of time, with rising income fertility has increased.

You can see this trend in the screen show above by following the course of the yellow bubble (U.S.) from the early 1990s to 2008. And note, further, that the screen shot captured by the freakonomists shows only 2008, not the upward trend over the prior 15 years. (Or the drop in birth rate during the recession, which implies a positive, not negative, correlation between income and fertility in the U.S.)

Why is that trend not shown in their analysis?

Perhaps because it would ruin their headline.

(But maybe I'm just seeing a correlation between bad analysis and eye-catching headlines, and assuming causality...)


To read the original post see: http://www.freakonomics.com/2011/06/10/the-rich-vs-poor-debate-are-kids-normal-or-inferior-goods/
Or a useful summary by the NY Times.
Or build your own Gapminder plot.