"When time is the numeraire in a social evaluation of public projects, life expectancies are essentially the unit of account.  Since different generations have different life expectancies, pursuing intergenerational equity requires discounting the extra time that future generations are likely to obtain.  The result is a Social Discount Rate set by the growth rate in life expectancies.  This is called the Life Expectancy Discount Rate (LEDR).  After providing estimates of the LEDR for 120 countries, the paper discusses some of the implications of using this rate." (SUMMARY IN FRE AND GER)