MEDLINE users, usage and economics.

The on-line services of the National Library of Medicine (NLM) have grown in terms of both numbers of institutions using the service and in terms of total service provided. About 10 billed institutions are added per month with a total of 675 such institutions at the end of 1977. Total searches have now reached 900 000 per year. NLM services account for about 45% of all the bibliographic searching in the US. The effect of prices has been significant.