Teenagers account for about 20% of the women of reproductive age in the US. Even steep declines have a marginal effect on overall fertility. Preganacies did fall by 71% considerably higher than any other group. The 30-34 year olds only declined by 1%. Those over 35 increased preganacies by 9%. Many factors are known to influence fertility. A recent, often quoted, paper gives one explanation for the teens. It suggests an incremental effect of smartphones particularly on the youngest cohort.
International Comparisons
The US data shows an interesting trend. Teenage pregnancies were relatively stable in the five years before 2007. In 2007 the trend line has a kink and the decline accelerates. The paper looks at 168 different countries around the world. It finds a similar acceleration in the decline in teenage pregnancies. Particularly in the more affluent countries. The pattern is the same but the kink appears in different years. The team then corrected for the roll out of broadband and 3G/4G infrastructure. They looked at the penetration of smart phones. The patterns then overlapped exactly. For the 19 most affluent countries the pattern was very close to the USA.
They point out that:
“The near universal timing of the break across countries with fundamentally different healthcare, welfare, economic and cultural environment point to a common global technological shock”
Hudson & Boedo 2026
Detailed Analysis of the USA
The USA is divided into 3135 different counties. For each county they were able to assemble data on teen birth rate and abortion rates. To this they added broadband infrastructure, mobile data coverage and smartphone ownership. They added many other factors known to explain fertility declines. This included things like religion. All between 2003 and 2020. The rollout of Web infrastructure was highly variable. It depended on the economic and physical characteristics of each county. They could therefore track changes in pregnancies as smartphones rolled out.
In this case they could look at the kink in the trend line correcting for other possible factors. They showed that young people were not just delaying pregnancies. The financial crisis and the opioid epidemic had no effect. There was something else going on.
Why did the trend have a kink?
Their argument is an interesting one. Teenagers especially want to be where everybody else “hangs out”. Before the tipping point “unstructured social time” was spent face to face. When more people were on line than off there is a break point. Everybody then migrates online. They can show that the tipping point occurs when more than half of teenagers are on line and using social media.
There is evidence from time use surveys to support their case. In 2004 45% of US teens owned a cell phone. By 2006 that reached 63%. In person socializing fell from 68 minutes per day to 38 minutes. “Computer leisure” including social media, texting and games rose from 22 minutes per day to 96 minutes. ( interestingly television viewing fell from 152 minutes to 72 minutes.)
It is “unstructured time” that the smart phone soaked up. Time spent in structured team sports remained constant. ”Meeting friends in person” fell from 50.3% to 34.9%. Even driving licenses for 16 year olds fell. The loss of that face-to-face time seems to have caused sexual activity to decline. The share of teenagers that had intercourse fell from 47.8% to 38.4%. There is 0.97% correlation between teen birth rate and in-person socializing.
What Does It Mean?
The greater decline in teen pregnancies is universal. This suggests that this is an additional factor to the general fertility decline. The detailed county analysis in the US suggests a causal effect. Declines follow the growth of smartphones and social media usage. The kink comes when a tipping point is reached. A replication in the 294 local authorities in the UK showed the same results. The results are so similar that the two curves completely overlap.
In other Newsletters I have suggested that one explanation for general fertility decline is the absence of “coupling”. People are not teaming up with a partner as much. There is no study yet to test whether the behaviours learned as a teen carry over into later life. US teen abortion rates were as high as 30%. The smartphone may have helped reduce the numbers. Researchers are however looking at other negative effects. For example, they are exploring smartphone roll outs and the impact on teenage suicides. This may be more related to the online content than is the case with preganancies.
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