A REPORT last year by the Milken Institute found a gaping disparity between the Philadelphia region's strength in the life sciences overall, and the "vitality" of its life-science start-ups. With a low birth rate and high death rate for small life-science companies, the region came in ninth in the start-up ranking nationally. Milken's analysts said that future growth in the life sciences - a sector that now accounts for one of every six jobs here - depends on "smaller, nimbler and more specialized firms."

Rankings in the life sciences, overall

1. Boston

2. Greater Philadelphia

3. Greater San Francisco

4. Greater New York

5. Greater Raleigh-Durham

6. Greater Los Angeles

7. Chicago

8. San Diego

9. Minneapolis

10. Washington, D.C.

11. Seattle

Rankings for start-up "vitality"

1. Greater Los Angeles

2. Greater San Francisco

3. San Diego

4. Boston

5. Greater Raleigh-Durham

6. Washington, D.C.

7. Greater New York

8. Chicago

9. Greater Philadelphia

10. Seattle

11. Minneapolis

Source: Milken Institute