The metropolitan areas of Boston, Massachusetts; Philadelphia, Pennsylvania; and San Francisco, California, continue to lead the United States in sustaining and building their life-sciences sectors, according to a report from the Milken Institute, a think tank in Santa Monica, California.

The Greater Philadelphia Life Sciences Cluster 2009: An Economic and Comparative Assessment finds that Boston is ahead when it comes to research and development capacity and in success at getting funding from the National Science Foundation for submitted proposals. Greater San Francisco leads in the availability of risk capital and in relative growth.