Math in economics papers: An explanation of an interesting trend in the data

Justin Wolfers links to a new paper presenting the upward trend in the number of equations per paper in economics. Here are two figures from that paper:

Source: Espinosa et al., 2012

What's your reaction?

Wow - big growth in the number of equations!

Yes, definitely (and I think that's almost certainly a good thing although of course how its done needs to be approached with care).

But I was also struck by the decline in equations after 1980 even though the trend in econometric output kept going up during that period. What is causing that?

My theory: that may be the impact of New Classical and Real Business Cycle economics.

It's just a thought. If you think about pre-New Classical stuff as being big systems of equations it seems to make sense. That would taper off with New Classical work. My sense is that a lot of the bigger DSGE type stuff is done in central banks and not necessarily put in articles, although to the extent that it is that happened later and may explain the trend picking up again.

Or I could be completely wrong. But I found that dip interesting. I *quickly* searched the article and did not see an explanation for the break in 1980.