Friday, April 8, 2016

Update: Births to "Older" Mothers Still Not News

This is an update of a post that originally appeared here in February 2013.

Sometimes "common knowledge" is not knowledge at all...

There has been considerable hand-wringing in the press over births to women over the age of 35. According to the Telegraph, older mothers are "driving up the birth defect rate." The New Republic suggests that older parents will "upend American society." And Slate, generally progressive, bemoans the "feminist fertility myth."

As a demographer, I am aware that birth rates in age groups 35-39, 40-44, and 45+ have been rising since the late 1970s for ages 35-39 and 45+, and since the early 1980s for the 40-44 set.

But as the granddaughter of a woman who birthed her youngest child when she was nearly forty, my skeptic antennae went up. My grandmother may have been a singular woman, but she was hardly a statistical aberration.

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 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.

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 data 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 1935-2010 (the most recent year for which complete data are available). The historical birth rates (births per 1,000 women) are shown in the chart below.

Zeroing in on ages 35 and older, to show more detail on the chart scale, we see that birth rates are indeed higher in 2010 than they were in 1970. Specifically, birth rates are 45% higher for ages 35-39, 26% higher for 40-44, and 40% higher for ages 45-49 in 2010 than in 1970.

But we do not need to go back very much farther to find a time at which birth rates were higher than they are today: In 1965 birth rates were higher for all ages 35-49 than they were in 2010.

If we go as far back as 1920, birth rates were nearly twice as high for ages 35-39, were three times higher for 40-44 year olds, and were more than 5 times higher for ages 45-49 than the rates in 2010.

In short, the phenomenon of increasing birth rates for women in their late 30s and 40s is as much a return to historical patterns as a deviation from them.

To be clear, some pregnancy risks do increase with advanced maternal age:
"older age strongly increases a woman's chances of at least three untoward outcomes—namely, stillbirth, miscarriage, and ectopic pregnancy" (Stein and Susser 2000)
However, there is considerable evidence that socio-economic factors play the most important role in birth outcome - perhaps far outweighing the age effects (Cohen 2012, Azimi and Lotfi 2011, Stein and Susser 2000).

As for the current focus on trends in the past four decades, I suspect the ease of collecting data from 1970-present is partly the cause of the focus on a "huge" increase in childbearing at older ages... when, in reality, rates have fallen if you look back just 5 years more.

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

Friday, October 30, 2015

Scary stats for Halloween 2015


There were an estimated 41.2 million potential trick-or-treaters (children age 5-14*) in the United States in 2014, unchanged from 2013.

But Halloween is clearly not just a children's holiday. 157 million Americans of all ages will be celebrating Halloween this year, with total spending reaching nearly $7 billion.

The average American adult will spend $74 on decorations, costumes and candy, down a bit from $78 last year, and well below the peak of $80 per person in 2012.

For those who will dress up to celebrate the holiday:
The most popular children's costume: Princess.
The most popular adult costume: Witch.
Should we read anything into that dichotomy?

The breakout costume star of 2015 is... "Star Wars character," which didn't crack the top 10 last year, but ranks 5th this year.

Sources: National Retail Federation and U.S. Census Bureau, Facts for Features
*Note: Of course, many other children - older than 14, and younger than 5 - also go trick-or-treating.


America's candy consumption in 2010 was nearly 25 pounds per person. If this candy were entirely Snickers bars, it would be the equivalent of nearly 4 candy bars, per week, per person. The volume of candy consumed, much like home prices, peaked in the middle of the decade, dipped at the start of the recession in 2008, and increased slowly each year since then. Another scary fact is that 2010 is the last year for which we'll have this data. Budget cuts led to the termination of the Current Industrial Reporting program.

American confectionery manufacturers produce about 35 million pounds of candy corn each year. That adds up to 9 billion candy corns - or about 30 kernels per person in the U.S.

For Halloween itself, Americans purchase nearly 600 million pounds of candy, spending nearly $2.6 billion for treats to hand out to trick-or-treaters.

Sources: U.S. Census Bureau, Current Industrial Reports, Confectionery: 2010National Confectioners AssociationDaily Infographic 2011 and 2012


According to Redfin (and contrary to what one might guess) homes near cemeteries sell for more, per square foot, than homes not near cemeteries.
"Redfin analyzed the price of homes less than 50 feet from a cemetery, and compared those to the price of homes less than 100, 200, 500 and 1,000 yards away. The numbers indicate that on average, homes near cemeteries are slightly smaller, but sell for more per square foot. On average, homes closest to cemeteries sold for $162 dollars per square foot, whereas the homes located more than 500 yards away sold for $145 per square foot."
But these homes were on the market for longer than their non-cemetery peers...


U.S. pumpkin production totaled 1.3 billion pounds in 2014, with a value of $145 million. In that year 50,900 acres of farmland were harvested for pumpkins. Those figures are likely to drop in 2015 as bad weather resulted in pumpkin crop losses.

Six states are pumpkin hotspots: Illinois, California, New York, Ohio, Pennsylvania and Michigan each accounted for more than 100 million pounds of pumpkins grown in 2010.

Canadian farmers grew more than 64,700 tonnes of pumpkins, valued at $23.2 million.

Sources: USDA National Agricultural Statistics and Statistics Canada Hallowe’en... by the numbers