Abstract: There are provided method, system and program for decreasing the amount of information by causing a distributor or user to determine a period for retention of digital information in advance and deteriorating digital information lowered in utilization value as the time elapses. The digital information is assigned with a compression ratio or a period for retaining the information amount (life). As the time elapses, old information is reduced in accordance with a degree of importance of the digital information. Deterioration has the meaning of erasing a predetermined item of the digital information or compressing the digital information through a predetermined method. By deteriorating the information, the information amount can be reduced.