1. A behavior estimation apparatus comprising: a memory to store behavioral statistical data including an occurrence probability of each of a plurality of different kinds of behaviors of a human during each time period, the behaviors including replaceable behaviors, each of the replaceable behaviors being capable of replaced with another of the replaceable behaviors; an input unit configured to input a plurality of conditions including a prediction period, and an annual consumption expenditure; an extraction unit configured to extract, from the behavioral statistical data, the occurrence probability of each of the behaviors within the prediction period as a prior probability distribution; an obtaining unit configure to obtain a consumption time ratio between the replaceable behaviors; and a calculation unit configured to calculate estimated occurrence probabilities of the behaviors which minimize a Kullback-Leibler divergence with respect to the prior probability distribution and satisfy a plurality of constraint conditions, the constrain conditions including (a) a first constrain condition that a ratio between estimated occurrence probabilities of the replaceable behaviors within the prediction period equals the consumption time ratio, (b) a second constrain condition that a sum of expenditures of the behaviors per unit time equals an expenditure per unit time calculated from the annual consumption expenditure, (c) a third constrain condition that a sum of the occurrence probabilities of the behaviors within the prediction period is “1”, and (d) a fourth constrain condition that a sum of the estimated occurrence probabilities of the behaviors within the prediction period is “1”.