So, the overall conclusion? If you believe in the IV approach, which many economists do, then 16 and Pregnant caused a significant reduction in teen births. If you don't believe in it, then watching more MTV is related to a significant reduction in teen births. Either of these is an interesting result in its own right.
Closer to home, New Zealand's teenage birth rate peaked at 32.85 per 1000 women aged 15-19 in 2008 and has declined since (to 24.89 in 2012; lower than the 29.4 in the U.S. in 2012). I wonder how many girls in New Zealand are watching 16 and Pregnant?James from last year's ECON110 class shared this story with me (from March last year), which I've been holding onto for a while:
Teen pregnancies are at their lowest in eight years and some experts think social media could be partly responsible.
Data from Statistics New Zealand has revealed the number of teenage pregnancies in New Zealand among women under 20 years old has almost halved since 2007 - the year that social media became a global phenomenon.
In 2007, 4955 women under 20 fell pregnant. But last year there were just 2865 births to under 20-year-olds and a large majority of those were to 18- and 19-year-olds.
Some researchers have credited the stark drop to better access to contraception, better sex education and better parenting.
Others, however, have suggested social media may have played a part.
A leading paediatrics expert, University of Auckland Associate Professor Simon Denny, said it was possible social media had contributed to a reduction in "risk behaviours" including teenagers having unprotected sex.
"What we have seen is this reduction and at the same time we have had this explosion in social media," Dr Denny said.
"There are some suggestions that young people are spending more time inside rather than going outside and engaging in risk behaviours but there is no hard evidence on this at this point.That, folks, is mistaking correlation for causation. While it makes a plausible story that teenagers are too busy on Snapchat and Instagram to have sex, the relationship may not be causal. Perhaps the causality runs in the opposite direction - teenagers are having less sex, so they spend more time on social media instead? Perhaps there is some third factor that has caused both an increase in social media use and a decrease in unprotected sex? Or more plausibly, perhaps these are just two trends that look like they're moving together but may actually be unrelated. If you doubt that the last of those would happen, try this highly significant correlation:
If you need any more, I suggest you go to Tyler Vigen's excellent site, spurious correlations (I particularly like that the number of movies Nicholas Cage has appeared in correlates highly with the number of drownings in swimming pools).
Anyway, on a more serious note, whether social media use and teen pregnancy are more than just spuriously correlated is an interesting research question. I'm sure a suitably motivated honours or masters student could dig into the data for New Zealand (and/or other countries) to find out.
[HT: James from my ECON110 class]