Life Expectancy in Developed Countries is Higher Than Conventionally Estimated. Implications from Improved Measurement of Human Longevity Dalkhat M. Ediev Received: 17 December 2009 / Accepted: 28 March 2011 /Published online: 12 April 2011 # Springer Science+Business Media B.V. 2011 Abstract Both the centuries-long tradition of conventional lifespan indicators and the more recent criticism to them ignore the true exposures of individuals to prevailing mortality levels. These exposures form a genuine part of a more comprehensive picture of the prevailing mortality conditions. In low-mortality countries, our estimated duration of human life exceeds the conventional estimates by 15 years. Our theory implies that mortality dynamics are characterised by a considerable inertia. This is used to develop new methods of forecasting, leading to a more optimistic outlook for future mortality. Keywords Longevity . Life table . Mortality . Life expectancy . Tempo effect Conventional indicators of human lifespan (Graunt 1661; Chiang 1984) are based on a hypothetical synthesis of the mortality conditions of different cohorts with (as yet) incomplete life histories. There is considerable ongoing debate about improvements to the traditional methodology under changing mortality rates (Bongaarts and Feeney 2002; Guillot 2006; Luy 2006; Wilmoth 2005; Rodriguez 2006; Wachter 2005). Improved measurement of the human lifespan is crucial for estimating prospects of longevity (Wilmoth 1998; Tuljapurkar et al. 2000; Oeppen and Vaupel 2002; Robine et al. 2006; Olshansky et al. 2009) and for understanding the implications of population ageing (Olshansky et al. 2009; Sanderson and Scherbov 2005; Lutz et al. 2008; Council of the European Union 2009). Here we show that both the centuries-long tradition of conventional lifespan indicators and the more recent criticism to them ignore the true exposures of individuals to prevailing mortality levels. These exposures form a genuine part of a more comprehensive picture of the prevailing mortality conditions. In low-mortality countries, our estimated duration of human life is about 95 years, which exceeds the conventional Population Ageing (2011) 4:5–32 DOI 10.1007/s12062-011-9040-x D. M. Ediev (*) Vienna Institute of Demography, Austrian Academy of Sciences, Wohllebengasse 12–14, 6th fl., 1040 Vienna, Austria e-mail: dalkhat.ediev@oeaw.ac.at