In order to determine the optimal copyright period Pollock started from the original premise of intellectual property laws, which means that the optimal period would be produce the maximum number of creative works. He then attempts to quantify factors such as the cost of production, ease and cost of copying both legally and illegaly, and ends up with an equation that suggests the optimal term of 14 years.
Before arriving at the 14 year figure, the paper starts by showing that the optimal copyright term drops as production costs fall and that in general it falls over time. The calculations and conclusions in the paper are based on analysis of various studies published in the US and UK over the last 10 years and cover subjects ranging from the effects of recent copyright extensions to file sharing among college students.
The paper can be freely downloaded in its entirety, and a brief overview is also available.
Source: Rufus Pollock
Here in the U.S., this lifetime + copyright system is ridicules. Amazing you could invent a cure to cancer and it would be yours for less than fifteen years. Write a book or movie or CD and it's yours forever.