For example, Evnine and Rudd (1985) use intraday data for a two-month period in 1984 and find frequent violations of boundary conditions and put-call parity for S&P 100 and Major Market index options, both of which are American options.(5) Evnine and Rudd further conclude that these options are significantly mispriced relative to theoretical values based on the
binomial option pricing model. Chance (1987) also finds that put-call parity and the box spread are violated frequently for S&P 100 index options and that the violations are significant in size.(6) However, these results may not indicate market inefficiency for several reasons.