Period life expectancy is the term you are looking for, I think. Immediate googling does not provide a helpful answer. Another interesting question would be Co

Period life expectancy is the term you are looking for, I think. Immediate googling does not provide a helpful answer. Another interesting question would be Cohort life expectancy of corporations - that is, have corporations started in the 1990's lasted longer than those started in the 2000's? (obviously, the graph of corporations in the 2000's would have less data)