Re: knowledge doubling

Robert J. Bradbury (
Sun, 29 Aug 1999 06:15:42 -0700 (PDT)

On Sun, 29 Aug 1999, Chris Watkins wrote:

> I've often come across statements such as "the quantity of human =
> knowledge is doubling every x years". However, x seems to vary from 2 to =
> 15, and nobody ever says where they get their figures from! Does anyone =
> have any pointers to information on the subject? (Or, for that matter, =
> any idea what the doubling period might be?)

I know, I've seen them too and they never quote a source. I suspect that librarians at a major university would know since they have to deal with the journal flow and they keep saying that it is rapidly increasing. A few years ago there was just "Nature", now there is Nature, Nature Genetics, Nature Biotechnology, Nature Neuroscience and Nature Medicine (perhaps more).

You can probably measure it 4 ways:

  1. Journal Article (page?) count
  2. Patent count
  3. PhD's awarded/Professor/Scientist count
  4. Research Budget $$$ (Government + Private industry)

There is no way those numbers are going to all agree. In the Medical field you can get a pretty good estiamte by going to PubMed (, reading the help topic on how to do a query by year, and then simply enter a query with no contraints except the year. Repeat that for each year from 1966 to now.

In the process of writing this I remembered that I had actually done this at one point (duh, I think my brain is too full...).

At any rate, pulling up the Excel sheet, and fitting the two curves to it gets:
Power Curve: y = 5E-05x^2.1719, R^22 = 0.9817 Exponential Curve: y = 31685e^7E-05x, R^2 = 0.9805 Where x = year and y = # publications in Medline.

If we have a statistician in the group, they may be able to translate that into "doubling time". The doubling time to go from 200,000 to 400,000 articles per year was 18 years. Just eyeballing it on a graph with linear scales, the growth looks pretty linear.

I suspect that biomedical publications closely matches the budget. I've got some of the NIH budget figures and have been meaning to plug them in and see how closely publication count matches $$ in, but haven't had time to do it yet. If true given the recent big boost in NIH funding, we should get a big publication boost in a year or two.