Prior to the stock market crash of 1987, Black-Scholes implied volatilities of S&P 500 index options were relatively constant across moneyness. Since the crash, however, deep out-of-the-money S&P 500 put options have become 'expensive' relative to the Black-Scholes benchmark. Many researchers...

In theory, by trading options, market participants asses and set future volatilities that can be identified using the Black-Scholes-formula in reverse. In reality, as regression analysis suggests, it is historical market data which instead are used to determine future values. Further analysis...

Results in this paper support evidence of time-varying beta coefficients for five sectors in Kuwait Stock Market. The paper indicates banks, food, and service sectors exhibit relatively wider range of variation compared to industry and real estate sectors. Results of time-varying betas...

This paper investigates sensitivity of U.S. natural gas price to crude oil price changes, using time-varying coefficient models. Identification of the range of variation of the sensitivity of natural gas price to oil price change allows more accurate assessment of upper and minimum risk levels...