How should life expectancy be calculated? More generally, how should life - bles be estimated? Since John Graunt s pioneering contribution, read before theRoyalSocietyofLondonat6p. m. onthe27thofFebruary1661, demog- phers have developed better and better methods. Some concerns were raised, including concerns about how to deal with heterogeneous populations p- lished in an article inDemography in 1979 that I wrote with Kenneth Manton and Eric Stallard. Yet, a few years ago nearly all demographers believed that as long as the underlying population and death counts were accurate, then lifetables...