Do we have any data about effectiveness of old science?

My usual link is to Human Accomplishment; Murray thinks that post 1890s or so there seems to be a downwards trend in how many figures of eminence there are per capita. This is masked by the simultaneous massive increase in world population and scientists. (He only calculates data up to the 1950s using reference books from the 1990s, which, along with his statistical techniques that escape my memory, hopefully attenuates or eliminates entirely questions about recency effects.)

(If you're interested, I have Human Accomplishment as an ebook.)

Independently of Murray, I believe I have seen mainstream articles to the effect that science over the 20th century has seen a striking increase in average number of authors per paper and similar metrics.

I'm not really sure I buy the low-hanging fruits argument. The 20th century has seen all sorts of new fields with tremendous low-hanging fruit. Look at computer science - it seems like everything in it was invented or thought about in the 50s and 60s and we are only just getting around to really implementing it all. And there seems to be similar problems in artistic fields (why would low-hanging fruits be exhausted simultaneously?). A quote-provoking quote for consideration from Tyler Cowen's Creative Destruction:

"The population of Renaissance Florence did not typically exceed 80,000 and at times fell well below that figure. To put the Florentine achievement in proper perspective with regard to population, consider that in 1984 approximately 35,000 painters, sculptors, potters, and art historians graduated from American art schools."