My spreadsheet compiling the last decade of Boston theatre is now approaching 500 productions. I worked on it last night.
It is getting a little harder as some theaters don't have their production history online and some list only the play titles without the authors. So I'll have to go back and fill in some of that information after researching it..
Chekhov is still up there, Moliere is gaining. Conor McPhereson (5), Richard Dresser (6), Harold Pinter (5) and Tom Stoppard (5) have rallied as well. Dresser has a relationship with Merrimack Repertory and they have produced at least four of his plays.