In 1981, Congress created the research tax credit to encourage U.S. businesses to do more research, thereby boosting their competitiveness in the world economy. The credit will expire in June 1995. In tax year 1992, corporation earned slightly more than $1.5 billion worth of research credits, most of it going to large manufacturing firms, particularly those producing chemicals, including drugs, motor vehicles, and machinery. Given a lack of data for evaluating the credit's net benefit to society, GAO has not taken a position as to whether the research credit should become a permanent part of the tax code or allowed to expire. GAO has concluded, however, that if Congress decides to extend the credit it may also want to ensure that the credit continues to provide an attractive incentive to most recipients at an acceptable revenue cost. One way this could be achieved it by requiring that the base be reviewed periodically and adjusted as needed.