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How many randomized trials are published each year?

Carl Heneghan
Last edited 17th March 2010

I thought it was worth re-examining how many randomized controlled trials (RCTs) are published each year. To determine the number this number per year I used the Medline (Pubmed) Trend database. The page displays the number of entries (articles) in PubMed (Medline) published every year which conformed to the following search strategy (randomized and controlled and trial).

The graph highlights the growth from 39 RCTs in 1965 to 26,017 in 2008. Some notable landmarks include the 1000 barrier being broken in 1976 and the 10,000 in 1994. Approximately every 10 years there is a doubling of the number of RCTs: 25,361 in 2007 versus 12,040 in 1997. At current rates we can expect to see 50,000 RCTs per year published by 2018-9.

RCTs per year

Breaking these numbers up by week you would have to read 500 RCTS per week in 2008 to cover the published RCTs in PubMed, the 100 barrier was broken in 1988. Per day it equates to 71 RCTs but I figured no-one submits and publishes on the weekend and if we consider only reading RCTS on weekdays then we have now have to read 100 RCTs Monday through Friday. To put this in perspective in 1980 you only had to read one RCT per day to cover all of the published RCTs. Today you have no chance of keeping up to date.

RCTs per week and per day

If you want to know how much is in PubMed in total. Well as of June 2007, approximately 1,000,000 items were archived and this is growing at 7% per year. Get reading quick!

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