Companies are slowlyโ€”very slowlyโ€”considering โ€œbinomialโ€ models for valuing stock options, instead of using the more simple Black-Scholes model. That’s according to a recent study by Aon Consulting, which found thatโ€”as of August 31, 2005โ€”122 public companies had disclosed they were using a binomial model, up from 36 companies that used a binomial model at the end of 2002.