Well, Scirus, the database of Scientific knowledge I've been using frequently on this weblog, has a lot of material relating to epidemiology. I feel a bit vulnerable relying on this source so heavily--if anybody has suggestions for freely available information, I will happily (well, grumblingly and slowly and swearing occasionally) replicate these searches on it.
Searching for epidemiology on Scirus returns 1,500,983 results. 315,678 of these are journal articles. 8,530 are patent results and the other million plus are 'other' web results. So, focusing on journal articles and patent results since 1920, let's see if the numbers double every 5 years.
Human knowledge (as expressed by journal articles published) about epidemiology has not doubled in the past five years. Only 106,722 of the 315,678 journal articles were published between 2001 and 2006. It's truly a triumph of the human mind, but it is not doubling. It is a compound annual growth rate (CAGR) of 8.85%, which would result in a doubling every 9 years. Looking at the time series, we see dips and lulls and a steadily progressive trend line, with a couple of jumps. When I get the graphs prepared, it will be easier to see.
Overall, CAGR for epidemiology is 6.22%, which doubles every 11.49 years. Overall growth in patents is 17.37%, which doubles every 4.33 years.
However, backing out the 2007 patents (198) leaves a total of 8,332. Of that number, 5,444 (65%) were filed between 2001 and 2006. So while academic investigation did not double in the past five years, commercial research and development more than did so. Indeed, epidemiology patents appear to have more than doubled in every five year period since 1987, when 19 patents were filed, a CAGR of 22.76%.
I suppose, if we treated one journal article and one patent as exactly equal, we could add them up and compare the totals. But, as I certainly don't have any reason to think that might be the case, I'm not going to. The figures are below if you want to do it, though.
Click below to see the data.