Implied Volatilities of the KOSPI 200 Index Option Market
Dam Cho
This paper aims to analyze implied volatilities(hereafter IVs), which are computed from the trading records of KOSPI 200 index option market from January 2005 to December 2014, to find out major charcteristics of the market pricing behavior. The data includes only daily closing prices of option transactions of which the daily trading volume is larger than 300 contracts, and the IV is computed using the Black-Scholes option pricing model. The empirical findings are as follows; Firstly, daily averages of IVs have shown very similar behavior to historical volatilities computed from 60-day returns of the KOSPI 200 index. The correlation coefficient of IV of the ATM call options is 0.8679 and that of the ATM put options is 0.8479 to the historical volatility. Secondly, when the moneyness, which is measured by the ratio of the strike price to the spot price, is very large or very small, IVs of call and put options decrease as the days to maturity get longer. This is a partial evidence of the jump risk inherent in the stochastic process of the spot price. Thirdly, the moneyness pattern shows heavily skewed shapes of volatility smiles, which is more apparent during the global financial crises period from 2007 to 2009. Behavioral reasons can explain the volatility smiles. When the moneyness is very small, the deep OTM puts are priced relatively higher due to investors¡¯ crash phobia and the deep ITM calls are valued higher due to investors¡¯ overconfidence and confirmation biases. And when the moneyness is very large, the deep OTM calls are priced higher due to investors¡¯ spike wish and the deep ITM puts are valued higher due to overconfidence and confirmation biases. Fourthly, for almost all moneyness classes and for all sub-periods, the IVs of puts are larger than the IVs of calls. And the differences of IVs of deep OTM pus ranges minus IVs of deep OTM calls, which is known to be a measure of crash phobia or spike wish, show positive values consistently for all sub-periods. The difference in the financial crisis period is much bigger than the others. This means option traders has stronger crash phobia in the financial crisis.
implied volatility,volatility smile,term structure of volatility,crash phobia,spike wish,jump risk,overconfidence,confirmation bias.