“Explosive” is the word routinely used to describe the growth of M.F.A. programs in creative writing. Iowa was the first, established in 1936. By 1994, there were 64. By last year, that number had more than tripled, to 229 (and another 152 M.A. programs in creative writing), according to the Association of Writers and Writing Programs. Between 3,000 and 4,000 students a year graduate with the degree; this year, about 20,000 applications were sent out.