Henriksson and merton ( 1981 ) regard the timing ability as a free put option . goetzmann , ingersoll and ivkovic ( 2000 ) try to catch the accumulated value of a sequence of such options . we conclude that gii model may pay a more applicable role in the timing study from the theoretical point of view 在对模型的构造进行深入的研究后，我们发现， tm模型假设时机选择使组合的系统风险呈非线性特征， hm模型将时机选择视为一免费的看跌期权， g模型进一步捕捉看跌期权在整个评价期间内的价值。
