Profit opportunities with the American put‐call parity when dividends are not expected

The objective of this research is to study borrowing and lending profit opportunities with the put‐call parity of American options when dividends on the stock are not expected. Studying profit opportunities embedded in the put‐call parity is intriguing because of their relative simplicity. The only assumptions necessary for the parity to hold are that option markets are frictionless and generate efficient prices of puts and calls around the underlying stock price. For this reason alone (parsimony of postulates) the put‐call parity is a tempting vehicle for studying option market efficiency. In this work it is shown that both synthetic lending and borrowing parities (before and after transaction costs), on average and ex post, have negative expected profits (i.e. put‐call parity implied rates are inferior to the observed riskless rate). When certain trading rules are established, however, empirical evidence of substantial profit opportunities with both lending and borrowing with the American parity (even after considering transaction costs) is observed. It is also shown that these opportunities are greater for some stocks than for others. The existence of these disparities might be an indication that the pricing mechanism of the respective options is not always in sync. The duration of disequilibrium between the options market and the stock market suggests that such occurrences are not just random bursts.