Simplify the following text for a Grade 12 native English-speaking person.
Original: He taught at Massachusetts Institute of Technology from 1977 â `` 1984 and from 1985-2000 at Harvard University , where he was the Louis Berkman Professor of Economics .
Simplified: He taught at Massachusetts Institute of Technology from 1977-1984 and from 1985-2000 at Harvard , where he was the Louis Berkman Professor of Economics .