Healthy life expectancy refers to healthy life expectancy for babies born in 1999 based upon an indicator, Disability Adjusted Life Expectancy (DALE), developed by WHO scientists. DALE summarizes the expected number of years to be lived in what might be termed the equivalent of “full health.” To calculate DALE, the years of ill-health are weighted according to severity and subtracted from the expected overall life expectancy to give the equivalent years of healthy life. Source : UNDP, Human Development Report