5 Things About Fertility Rates

Birth order is a hot topic in my family. I’m the oldest of four, and for as long as I can remember I’ve been grousing that being the oldest child is a bad deal. Your parents try out all their bright shiny untested parenting theories on you, relaxing the rules for all the subsequent kids, you’re held responsible for everything, and generally it’s just not faaaaaaaaaaaaaaaaair. Of course all this extra pressure does have some upsides later in life, like an increased likelihood of being a CEO or President. Anyway, given how often I’ve brought this up over the years, my parents (a youngest-of-3 and middle-of-5, respectively) were quick to point me to this article about the disappearance of the middle child in the US. After reading this article and the AVIs post about birthrates earlier this week, I went on a bit of a Google-bender on the whole topic. I figured I’d do a roundup of the most interesting numbers I found.

A quick note before I get started: for ease-of-counting purposes, fertility rates and family sizes are normally measured by “number of kids per woman”. This makes the data less messy, since you don’t have to worry about controlling for people who have children with multiple partners. However, it does often make discussions of fertility rates sound as though women are having kids in a vacuum and that men have nothing to do with it. This is simply not true. Social and economic pressures that encourage women to have fewer kids are almost certainly impacting men as well, and the compounding effect can decrease birthrates quite quickly.  So basically while I’ll be making a lot of references to women below, that’s just a data thing, not a “this is how it actually works” thing. Also, I’m going to mostly stick to numbers here as opposed to speculate on causality, because that’s just how I roll.

Alright, with that out of the way, let’s get started!

  1. Birthrates are declining worldwide. It’s not surprising that most discussions of birthrates and family size in the US immediately start with a discussion of the factors in the US that could have led to falling birthrates. However, it’s important to realize that declining fertility rates is a global phenomena. Our World in Data shows that in 1950, the total fertility rate (TFR) for women everywhere was 5 children. In 2015, it was at 2.49. In that same time period, the US went from about 3 children per woman to 1.84.  This is notable because sometimes the explanations that are offered for declining birthrates in the US (like expensive daycare or lack of parental leave policies) don’t hold when you compare them to other countries. Sweden and Denmark are both known for having robust childcare/time off policies for parents, yet their fertility rates are identical to or lower than ours. Whatever it is that pushes birth rates lower, it seems to have a pretty cross cultural impact.
  2. Birthrates can fall fast. Like, really really fast. Growing up in the US, I always thought of birthrates as something that sort of slowly trended downward as countries grew more developed. What I didn’t realize is that it doesn’t always happen this way. Our World in Data has an interesting chart that shows how long it took for various countries to go from a birthrate of 6 or more children to 3 or fewer:  What’s stunning about this is that some of these numbers are half a generation. For birthrates to fall that quickly in Iran for example, it doesn’t just mean women were having fewer children than their mothers, it means they started having fewer children than their older sisters. In case you’re curious if these trends were just a product of instability in those countries during those times: today the birthrate in Bangladesh is 2.17, South Korea is 1.26, China is 1.60, Iran is 1.97 (per Wiki/CIA Factbook). It seems like all the downward trends shown here kept up or accelerated. China obviously made this a formal policy, but it does not appear the other countries did. I found this interesting because we often hear about subtle factors/cultural messages that impact birthrates, but there’s nothing subtle about these drop offs.
  3. A reduction in those having large families impacts the average as much (or more) than the number of women going childless. One of the first things that comes up when you talk about dropping fertility rates is the number of women who remain childless. While childless women certainly cause a drop in fertility rates, it’s important to note that they are also lowered by the number of women who don’t have large numbers of kids. I don’t have the numbers, but I would guess that the countries in point #2 ended up with lower fertility rates not because of a surge in childless women, but by a major decrease in women having 6 or more children. If we look at the change in family size in the US since 1976, the most notable drop is women having 4+ kids. From Pew Research:My first takeaway from this is that the appeal of having 3 children is timeless. My second takeaway is that it appears a large number of people aren’t crazy about having a large family. This matches my experience, because while you often hear people ask those without children or with one child “why don’t you have more kids?” you don’t often hear people ask those with 2 children the same thing. My friends with 3 children inform me that they actually start getting”you’re not having more are you?” type comments and I’d imagine those with 4 or more get the same thing routinely. Now I grew up going to Baptist school and my siblings were all home schooled at some point, so I am well aware that there are still groups that support/encourage big families. However, even among those who like “big families”, I think the perception of what “big” is has shrunk. I have friends who talked incessantly about wanting big families, married early and were stay at home moms, and none of them have more than 5 children. Most of us don’t have to go more than a generation or two back in our family trees to find a family of 5 kids or more. It seems like even those who want a big family think of it in terms of “more children than others” as opposed to an absolute number. Yes, the Duggars exist, but they are so rare they got a TV show out of the whole thing.
  4. International adoption likely doesn’t get factored in. As mentioned above, I probably know an above average number of people with 4+ children. Many of these families have a mix of biological and adopted children, frequently foreign adoptions. According the the CDC though, it doesn’t appear those adopted children are not counted in birthrate data, as they calculate that off of birth certificates issued for live births taking place in the US during a given year. Now of course this isn’t a huge impact on overall numbers: there are currently only about 5,000 international adoptions/year in the US, down from a high of 15,000 or so, vs 4,000,000 overall births. However, it is interesting to note that “number of kids” does not always equal birthrate. Since the US is the biggest adopter of foreign children in the world, it is a thing to keep in mind here.
  5. The demographics of who doesn’t have kids are changing When you mention “women without children” the vision that immediately springs to mind is a well educated white woman who put her career first. Interestingly enough, this stereotype is increasingly untrue, and is changing in many countries. According to Pew Research, childlessness among women with post-graduate degrees has dropped quite a bit in the last 20 years, and the number of women in that group with 3+ kids has gone up:According to the Economist, in Finland women with a basic education are less likely to have children than their more educated peers, and other countries are trending the same way. The US is nowhere near flipping, but it is an interesting trend to keep an eye on. Historically, education has always been associated with dropping fertility rates, so this would be huge if it switched.

Overall, I thought the data out there on the topic was pretty interesting. The worldwide trends make it interesting to try to come up with a hypothesis that fits all scenarios. For example, we know that effective birth control must impact the number of children people have, but Britain and the US both had birthrates under 3 decades before oral contraceptives came in to play. Economic resources must play a part, and yet it’s the richest countries that have the lowest birthrates. Wealth is sometimes linked to higher numbers of children (particularly among men), but sometimes it’s not. Education always lowers fertility rates, except that’s started to reverse. Things to puzzle over.

From the Archives: How Often Does SCOTUS Agree?

With all the talk about Supreme Court nominations going on, I thought I’d take this opportunity to revisit a post I did back in 2012 about the level of agreement between Supreme Court Justices. I wrote the post because there seemed to be a perception that the Supreme Court was deeply divided, when the reality is that the most common outcome is a 9-0 decision. I got my data from the very cool SCOTUSblog Stat Pack, and they’ve kept putting them out every year since I posted. They now have 7 years worth of data, so I decided to make a graph of how often the Justices agree each term:

As you can see, the unanimous decision is still the most common outcome, with the 8-1 decision generally being the least common.

Back in 2012 (at the end of OT11), I mentioned that Roberts and Kennedy were the most likely to vote with the majority. Per the stats, they still are. At the time, Ginsberg was the most likely to dissent, now it’s Sotomayor.

The justices most likely to agree are Ginsberg/Sotomayor and Alito/Thomas, and the justices least likely to agree are basically the same, but with the partners swapped. Even the justices who agreed the least agreed 50% of the time on disputed cases. When you add in that half of all cases are unanimous, that means our most dissimilar justices agree 75% of the time.

To note on the above stats: SCOTUSblog breaks this down by both all cases and non-unanimous cases, and it basically doesn’t change. Focusing on just 5-4 cases changes things a bit, but that’s mostly because there’s so few of them.

They also did a round up on just 5-4 cases, and the influence Kennedy had over the years. Here’s the graphs they put out:

I’ll be interested to see who the next Justice is, and if the way the cases are decided change substantially. In evaluating the impact of any change though, we have to have a sense of what the baseline is. Thanks to SCOTUSblog for making that easier.


What I’m Reading – July 2018

Hey hey! I’m back from Juneau and a brief stop in San Diego, and life is good. The wedding was great, the bride gorgeous, and I made it through my toast/maid of honor duties/boat ride to the venue without an issue. Juneau was as lovely as promised, and we had a great time.

I have to say though, I have never been to a place with less predictable weather than Juneau. Ever single day we were there it said it would be 60 degrees and raining, yet the temperature would vary wildly and the amount of time it rained was highly uneven. Sometimes “rain” meant 30 minutes, sometimes hours. One of the groomsman told me that if you predicted rain in Juneau every day, you’d be right 2/3rds of the time.  Of course I looked this up and discovered that it’s pretty much true.

Quite the leap to go to San Diego right after, where if you predicted sun every day you’d also be right about 2/3rds of the time. Also, San Diego is a borderline desert with 12 inches of precipitation a year, and Juneau gets enough rain to make it a rain forest (77 inches) and a healthy dose of snow (78 inches). For reference, Boston gets 43 inches of rain/year (close to the national average of 39) and 44 inches of snow.

Other than weather reports, I enjoyed this article about some recent discoveries that shed some light on human sacrifice practices among the Aztecs. Much of our information about human sacrifice comes from the Conquistadors, and there have always been questions about how accurate they were, given that they used it to justify a lot of their own killing. Recent discoveries suggest that the practice may have been quite widespread in the capital, as a whole temple of skulls was discovered. Sounds like the start of a horror movie to me.

This article about Crossfit covers a lot of ground, but the accusations of scientific fraud were pretty interesting to me. Basically, for several years Crossfit employees had been accusing the National Strength and Conditioning Association of publishing/sponsoring bogus papers designed to make Crossfit look bad because they were a rival. Some of their accusations sounded like the stuff of conspiracy theories, until a few lawsuits proved they were actually right. Now three papers alleging problems with Crossfit have been retracted, and internal memos from the NSCA show they did consider Crossfit a rival, and that they did encourage paper authors to put more negative data in their papers. Unfortunately for the investigators, they now can’t produce how they got that data, and the papers have been yanked. It sounds all good for Crossfit, until one of the employees who led the charge started tweeting anti-LGBT things and got fired. Still an interesting and troubling case for those concerned about scientific integrity.

This is old, but I had no idea NASA scientists ranked the least/most realistic science fiction movies back in 2011. It came up because Jurassic Park was #6, and we were talking about the De-extinction Project.

The AVI did not like my “50 Songs for 50 States” link in the comments section on my Alaska post, so I started looking around for other versions. I found a few other versions, but it occurred to me I’m judging all of the lists off of what they list for Massachusetts and New Hampshire. Really I think Ben just needs to write one of these. In the meantime in honor of our heat wave, here’s a song about summer in New Hampshire that’s better than the of the picks on any of these lists:



The Carlisle Method: One Year Later

Every once in a while the traffic on an old post goes through the roof, and I realize something interesting must have happened. This week it was my Carlisle Method post, which I appreciated because I had been meaning to check back in on that whole situation.

For those of you who didn’t read the initial post, here’s the overview:
An anesthesiologist came up with a neat statistical way of checking for data fraud. Rather than focus on the flashy results and conclusions of papers, he focused on the characteristics of the test group vs control group and looked for evidence that they weren’t random. The theory is that people committing fraud would mostly focus on their conclusions, but might get sloppy when reporting things like subject age and such.  He publicly named the papers he thought were most questionable, and investigations were launched.

A year later, some of the results are in. The New England Journal of Medicine announced their results, and they actually are a bit encouraging. Out of the 11 papers they analyzed, 5 had mislabeled “standard error” as “standard deviation” so the Carlisle Method was picking up on the error. 5 papers were reviewed and found to be okay, and they suspect some limitations in the Carlisle Method itself had wrongly flagged them.

One paper however, is getting lots of attention. It turns out that a major paper on heart health and the Mediterranean Diet wasn’t quite done as reported. While it had been reported as a randomized trial, a bit of digging showed that about 20% of its participants  were actually “cluster randomized”.  The authors reanalyzed the data using the remaining 80% of people, and noted that this didn’t change the conclusions, but it did make them less statistically compelling. The paper was retracted and replaced with a new version that correctly covers the methods.

Now all of these errors may appear to be small, but they do raise a bit of a cause for concern. There is an assumption that all statistics will be checked thoroughly before papers go to press, but I think this highlights that sometimes errors get through. Particularly if a paper has a big splashy finding, it’s possible that errors will not be reviewed. The NEJM shared this concern, and is implementing a statistics course for their editors and giving extra scrutiny to published papers.

More concerning than the NEJM’s findings however, is that the other 7 journals who had papers on the list haven’t completed their investigations yet, said there were no problems with any of the papers, or didn’t respond. It seems a little unlikely that only the most prestigious journal involved had any errors, so it’s unfortunate the other journals aren’t doing more.

More on the varied reactions to the Mediterranean diet study here and here.

Off to Alaska

I’m off to Alaska shortly, to see my sister get married. I’ve never been before, and I believe this trip puts me up to 31 states visited. Here’s my map:

(Map drawing here)

Road trips from Massachusetts to Georgia and one from San Diego to Seattle got me the coasts, and a surprising amount of my midwest experience is from various conferences. Alabama, West Virginia and Alaska are the states I will have visited solely to watch someone get married, though I got to/will get to take a good look around each before leaving. With any luck I’ll add Nebraska to my list in September.

Amusingly, my 5 year old son has never been outside of New England, and Alaska will be his first experience with the rest of the US.

I looked it up, and apparently the average American adult has been to 12 states, with Florida, California, Georgia, New York and Nevada being the most visited. The map of visitation is here:

In many ways my map reflects the average, though my time in New England snagged me all the rarer states there.

Overall I’ve loved every new state I’ve been to, and I expect to enjoy Juneau quite a bit. The plane ride with a 5 year old may be tough, but the end result should be awesome. Wish us luck!

Vitamin D Deficiency: A Supplement Story

I think I mentioned a little while back that I hadn’t been feeling so great and was going to slow my posting down for a bit. A decent amount of that “not feeling great” thing was related to a rather alarming Vitamin D deficiency I had unfortunately developed, and have since been treated for. This involved taking prescription strength megadoses, which helped almost instantaneously. It was lovely. As my doctor said “this is the best possible outcome. You came in with all sorts of symptoms and one simple thing fixed it.” I fully agreed.

It was an interesting thing to have happen because a few years ago another family member of mine had asked their doctor for a Vitamin D test and gotten an eye roll and a “that’s not really a thing we do any more”. Googling a bit, it seemed like there were nearly as many articles talking about how you shouldn’t take Vitamin D as those advising that you should. In classic “vitamins as fads” fashion, I noted that most of the pro-Vitamin D articles were from around 2010, and the anti-ones were much more recent. Combining my own experience with that of Dr Google, it got me thinking about how trends in supplements (or other medications or health behaviors for that matter) get going and why people then turn on them.

Step 1: Something that is under-recognized makes people feel terrible.

According to the American Association of Family Physicians, Vitamin D deficiency can result in “Common manifestations of vitamin D deficiency are symmetric low back pain, proximal muscle weakness, muscle aches, and throbbing bone pain elicited with pressure over the sternum or tibia.” Me? I had all of those symptoms. It sucked. I couldn’t sleep. Doing any activity left me sore and tired.

Now since Vitamin D deficiency is pretty well known, my doctor tested for it right away along with several other things. However, if it was not a well recognized deficiency and she had to fumble around a bit before she got there, I could have been living like that for months or years.

Step 2: People who feel terrible feel better, and are excited about their miracle cure.

Now I am pretty darn excited about my turn around on Vitamin D, as I think anyone would be. Again though, Vitamin D is a pretty well known deficiency, and lots of people I talk to have had the same experience or know someone who has. Thus, my compulsion to “evangelize” this solution is limited. A bad thing happened, the medical establishment addressed it immediately, and I am a happy camper. No real story there.

However, if I’d been feeling that way for months and my doctor had overlooked it, I’d want EVERYONE to know what happened to prevent the suffering of others.

Step 3: People who hear about this start to wonder if it’s their issue too.

Lots of people feel fatigued, or have aches and pains. The number who might hear my story and wonder if this Vitamin D deficiency were causing their might be much wider than the circle who would go in to their doctors and complain of the same thing. This isn’t bad, but it does mean that some of those people are going to have much milder symptoms than the ones I experienced, and those could be something else.

For example, what finally drove me to my doctor was being in so much discomfort that I was barely sleeping at night. I walk to and from the train every day (about 1.5 miles each way), and for a variety of reasons (including a weekend) I skipped about 4 days. When I started walking again, I was so sore I could barely stand when I got home. I felt like I’d run a marathon. That’s when I realized something was SERIOUSLY not okay. I’d been ignoring aches and pains for a few months, but you can’t ignore that.

So my issue got so severe I had to pay attention, but those who I tell about it are sort of having the information solicited. Two different groups.

Step 4: Some people figure if some is good than more is better.

There’s a lot of debate over what an optimal Vitamin D level is, but it will not surprise you to know that I was not in the grey area. I found this chart (unfortunately no source) that shows some of the controversy:

For reference, my level was 12. No one appears to debate that I needed treatment.

The controversy has arisen over some of those in between groups, like those in the 20-40 range. Some people say that they need more, but if they lack clear symptoms and hover around 35, is that really true?

To take it a step further, some people with aches and pains just start taking Vitamin D assuming that they are deficient with no testing at all. This is where things start to go off the rails a bit.

Step 5: The backlash

Okay, so now we’ve got people on supplements for levels that may or may not be dangerous, and bottles flying off the shelves at stores to treat people who may not have a deficiency. That’s when some people start to say “okay, pump the brakes here”.

What was a miracle cure for people with clear symptoms and a definitive deficiency now moves to something of questionable benefit for many many others. That’s when you get doctors who start eyerolling at things, rightly or wrongly.

Now all of this isn’t to say that I object to supplements, or people trying to find things that work. I don’t. That’s a good thing.  However, for whatever reason, we do seem to forget that many supplements or medications are only miracles when someone is really not doing well. If you look at the controversy over statins for example, it’s clear that much of it got stirred up when doctors started prescribing them to people with very few risk factors. The evidence that they work for those with high risk of heart attacks or stroke are pretty good, the evidence that they work for people with low risk is not great. I think we all want to believe that something that can take someone at high risk/severe pain back to normal will help those with mild risk/mild pain get back their too, but it doesn’t always happen that way.

I think this comes back to our weird tendency to assume all relationships are linear. Just another reminder that you can’t assume that. Now excuse me, I’m going to get a bit of sun.

On Accurate Evaluation

It’s no secret that I have a deep fascination with people’s opinions about “popular opinion”. While sometimes popular opinion is easy to ascertain, I’ve noticed that accurately assessing what “most people know/believe” is a bit of an art form. This is particularly true in the era of social media hottakes, all of which seem to take the form of “this thing you love is terrible” or “this thing you hate is actually great”.

I have such an obsession with this phenomena that I gave it a name (the Tim Tebow effect) which I define as “The tendency to increase the strength of a belief based on an incorrect perception that your viewpoint is underrepresented in the public discourse”.

I was thinking about this recently after reading the Slate Star Codex post on the “Intellectual Dark Web” called “Can Things Be Both Popular and Silenced?” In typical SSC fashion it’s really long and very thorough, and basically discusses how many different ways there are of measuring things like “popular” and “silenced”. For example, Jordan Peterson appears to make an absurd amount of money through Patreon ($19-84k per month by this estimate), so in some sense he is clearly popular. OTOH, he has also had threats made against him and people attempt to shut down his lectures, so in some sense there are also attempts to silence him. It’s this tension that Alexander explores, and he covers a lot of ground.

Given that my brain tends to uh, bounce around a little bit, this essay got me thinking of another topic entirely: the situation of women in the Victorian Era.

This connects, I promise.

Anyone who knows me or has seen my Kindle knows that I have a very bad habit of acquiring an enormous backlog of books to read. It’s so bad that I keep a running spreadsheet of how much I should be reading each week, because of course I do, and I tend to be flipping between at least a dozen at a time. Recently I picked up two I’d had hanging around for a while Unmentionable: the Victorian Lady’s Guide to Sex, Marriage and Manners and Victorian Secrets: What a Corset Taught Me about the Past, the Present, and Myself. I had thought these two would go well together as they appeared to be on the same topic, but they ended up being almost diametrically opposed.

Unmentionable took the stance that we all (or at least women) idolized the Victorian era, and it’s stated goal was to make us realized how bad it actually was. Victorian Secrets OTOH took the stance that we all thought too little of the Victorian era, and wanted to explain some of the good things about it.

I spent a lot of time mulling those two statements, and ended up deciding that they really both had some truth to them. In Unmentionable, she talks about how Jane Austen movies make it all look like romance and pretty dresses, which is a fair charge. Her chapters on how those pretty dresses were never washed, and how you’re not taking a shower or washing your hair much, and how unsanitary most things are was pretty interesting and made me quite grateful for modern conveniences. In Victorian Secrets, the author wore a corset for a year and ended up wearing lots of other Victorian clothes, and mentioned that the corset had gotten a rather unfair rap. She had done a lot of research and had some interesting points about how Victorian’s weren’t as backwards as they are sometimes portrayed. This also felt fair.

Interestingly, in order to make their points, both authors relied on different sources. Unmentionable stuck to advice from books and magazines during the era, and Victorian Secrets made the case that trying to mimic the habits of everyday people from an era was the path to understanding. I suspect both methods have their pros and cons. A person from the year 2150 trying to read Cosmopolitan magazine would get a very different impression of our era than someone who walked around in our (now vintage) clothing. Both would have truth to them, but neither would be the whole picture.

I think this ties in to all these discussions about “popular opinion” or “the general consensus”, because I like the thought that sometimes there can be competing popular opinions on the same topic. Pride and Prejudice is still a favorite book for many girls because they both love the romance and the feel of the era, while also disliking all the rules and the lack of choice for women. While I’m sure there are some women who either love the Victorian Era or hate it, I’d actually suspect that many women love the thought of parts of it and dislike others. Given that most of us have very little exposure to it outside of a brief mention in history class and our English Lit curriculum, it is entirely possible that the likes and dislikes could be somewhat ill informed. This actually leaves a good bit of room for authors to truthfully claim “your love is misguided” and “so is your dislike”.

Yet another way popular opinion gets slippery when you try to nail it down.

By the way, weird fact about me: I’ve never actually read Pride and Prejudice, only Sense and Sensibility. I think my high school English teacher was getting a little bored with P&P by the time I got there, and I never picked it up on my own. I’ve seen two film versions and I read Bridget Jones Diary though, so I pretty much got the gist.

Just kidding librarian/English teacher friends, adding it to my spreadsheet now.