Sperm problems aren’t depressing fertility rates. Well, not directly.
We know sperm issues aren’t causing fertility rate declines. Sperm can’t even be among the main culprits because infertility isn’t. The main reason people are having fewer kids, on average, is not that they can’t but that they don’t want to.
Infertility only impacts about 15% of hetero couples. In 20% of cases, the man is solely responsible. In up to 40% of cases, it’s both.
Another issue is that sperm issues don’t always harm fertility.
Thus, mathematically, sperm issues could only possibly account for a tiny percentage of the total fertility rate.
Sperm issues are still important. For example, they point to other health issues.
I also suspect that sperm issues are impacting the total fertility rate indirectly.
But before I make that case, let’s examine the evidence for and against the existence of sperm issues.
To make a long story short, in the 1970s and then again in the 1990s studies came out that pointed to a huge drop in sperm count and quality. The problem with these studies is that researchers back in the day were not very good at accurately counting sperm. So, I’d take any studies claiming huge declines since the 1970s with a grain of salt.
Another issue is where sperm studies often get their data. For example, 22.22% of the studies in this 2017 meta-analysis use fertility clinic data. Guess who tends to go to those?
Indeed, you tend to find stable sperm counts and quality when you only look at men who either don’t have known fertility issues or men who’ve ever knocked someone up.
However, newer studies do show that when you look at sperm donor samples rather than fertility clinic data, such as this 2024 study, you find declines in sperm count and quality between 2008 and 2021. Similarly, a 2018 study found declines in count and quality among sperm donors in several US cities between 2007 and 2017.
In my unprofessional opinion, sperm counts and quality are down in the US over the past 20, if not 50, years. And I think they’re down for similar reasons that obesity, erectile dysfunction, and low sex drive are up over the same period. I blame food additives, SSRIs, smoking, pollution, microplastics (BPA, phthalates), and other endocrine disruptors.
Now, here’s my theory of how all this relates to total fertility rates.
Most of the decline in fertility in the US over the past few decades is due to girls in their teens and women in their 20s having fewer or no kids.
From what I’ve read, heard, and can deduce, I’d describe a very large percentage of pregnancies among women under 30 as “semi-intentional.” Like, they’re less actively trying to have a baby and more not as actively trying to avoid it as they could be.
This is where sperm issues, along with obesity, erectile dysfunction, and low sex drive come in. Young people are having less sex today than in decades past. And they may be, on average, less fertile as well.
This seems like it would lead to fewer “semi-intentional” pregnancies.
At the same time, it might be hard for researchers to capture this in their data. First and foremost, many parents are understandably loathe to admit it.
Similarly, how many non-parents are going to cop to just being lucky or not getting laid that often or the fact that they can only ejaculate once per month, and it has to be into their own hand?
So, yes, I do think it’s plausible that male sperm issues are contributing to fertility rates. But only very indirectly.
In short, corporations are poisoning us. The entire planet, animals included, is becoming fatter and no one knows (corporations won’t fund researchers, departments, or schools who actually want to find out) why.
One symptom of the poisoning is that men are getting fatter, weaker, less horny, less potent, and less fertile.
Because men are getting fatter, weaker, less horny, less potent, and less fertile, fewer women are having “semi-surprise” pregnancies. And since such a large percentage of pregnancies have always been only kinda planned, a large drop in these kinds of pregnancies will have a big impact on the overall fertility rate.
My takeaways are twofold:
Anyone telling you fertility is down because X is wrong. We do not know why fertility is down. That person has only read or heard enough to be dangerous.
Anytime you hear someone speak confidently about how many kids people “want,” ask them what they mean. It’s not actually very simple or obvious. That’s I wrote that section in Why increase fertility when you can just allow more immigration?
I do wonder if there are also fewer women aiming for "semi-intentional" pregnancies in recent years too as professional class trends spread to the working class and poor.
Here's a little personal anecdote no one cares about but I'll share anyways.
When my wife and I had our first kid, I was obese, smoked cigarettes, ate like an animal, and didn't exercise. It took us 5 months to get pregnant.
When we started trying for our second, I had recently lost 70 lbs, ate a high protein, high fiber, low carb diet, had started going to the gym 3x per week, took regular walks, etc. On the first weekend where tests said she was ovulating, we had sex once (kids, ya know, they block you). She got pregnant immediately. Unfortunately it was a chemical pregnancy though. When we started trying again 3 months later, she ovulated, we had sex one time, and she was immediately pregnant. We now have a son.