"I would say a lot depends on job growth, because that's what drives rents. Boston and Cambridge are seeing pretty solid rent increases and some of the stronger suburban markets like Waltham and Burlington are as well. But we need to see what happens in some of the outlying submarkets like Chelmsford and Billerica before rents grow enough to spur any speculative development. Another factor to watch is construction costs, as they're rising steadily." Jay Dacey, president, Integrated Builders, Rockland, Mass.