To provide a statistic multiplex system that can assign a code rate suitable for the characteristic of people, a statistic multiplex controller, a statistic multiplex control method and a method for deciding a numerical expression in statistic multiplex control.

The statistic multiplex system 1 is provided with image encoders 2i that encode program data Si, a multiplexer 6 that multiplexes output data from the image encoders 2i, and a statistic multiplex controller 5 that assigns a bit rate to each of the image encoders 2i. The statistic multiplex controller 5 calculates a tentative bit rates TRi according to an expression TRi=M/(K+A/ Di), where Di is coding difficulty of the program data Si and M, K, A are constants, and decides a coding rates Ri on the basis of the tentative coding rates TRi.