请问一下，题目中所说的interest rate应该理解成real还是nominal？
计算保费时使用的是real interest rate=(1+nominal rate)/(1+inflation)-1 = (1+ real + inflation + expectation of inflation)/(1+inflation)-1
题目中如果说的是nominal rate, nominal rate降低，real rate不一定会减少，保费就不一定增加
设： real rate = 1， inflation =1， expectation of inflation=1， 计算出的real rate = 3/2
如果 real rate = 1， inflation =0， expectation of inflation=1, 计算出的real rate = 2
