volatility of ecnomic是什么意思?

英语翻译

the freight rate volatility in logarithm (ht) is defined as the one-step ahead conditional

volatility of freight rate from an AR-GARCH model,

英语翻译
The volatility parameter can be estimated either from historical data (historical volatility) or implied from the price of European options (implied volatility).In the first case,the length of the time series,the frequency and the estimation methodology may lead to different estimates.In the second case,as options differ in strike price,time to expiration and option type (call or put),which option class yields implied volatilities that are most representative of the markets’ volatility expectations,is still an open debate.Various papers have examined the predictive power of implied volatility extracted from different option classes.Christensen and Prabhala [3] examine the relation between implied and realized volatility on S&P100 options.They found that at the money calls are good predictors of future realized volatility.Christensen and Strunk [4] consider the relation between implied and realized volatility on the S&P100 options.