U(W) U(W2) U[pW1+(1-p)W2] pU(W,)+(1-pU(W2) U(Wi) pW1+(1-p)W2 W2 风险回避者的效用函数风险回避者的效用函数 W1 pW1 +(1-p)W2 W2 U(W) O W U(W1 ) U(W2 ) U[ pW1 +(1-p)W2 ] pU(W1 )+ (1-p) U(W2 )