5. What does the database represent?
If a low-mortality population is defined by life expectancy at birth of 75 years or more, about 780 million people, or 15 percent of the world population, enjoy low mortality. Of these, 755 million live in countries included in the database. However, the data for 277 million among them (in Canada and the United States) present considerable inaccuracies in age information, leaving 478 million in 19 low-mortality countries with essentially reliable data. The database includes further nine countries with a combined population of 102 million for which the information is judged good or acceptable; in them the life expectancy varies from 70 to 74 years. Thus the fully utilizable information covers 28 countries with a total population of 580 million in 1990, all with a life expectancy of at least 70 years.
The database may therefore be considered representative of today's low-mortality nations which it depicts in their appreciable variety and not as a uniform population. In fact, it will be seen that it has not been possible to go very far even in forming groups of countries with distinct scenarios. The spearhead of longevity is no doubt represented in the data and so are cases of various degrees of delay and stagnation in mortality reduction.
There is uncertainty as to the level of old age mortality in Canada and the U.S. but we have seen no valid evidence to assume that it in either of them falls outside the range observed in the 28 countries here described.
The population in the group of 28 is relatively aged so that while it makes up only 11 percent of the world's inhabitants, it comprises an estimated 30 percent of the 80-and-over and probably more than 40 percent of the world's centenarians.
To conclude this chapter with a word about the volume of data, the evidence from the 28 countries is based for the 1950-89 period on 68 million persons aged 80 and over of whom 51 million had died and 17 million were alive on 1 st January, 1990.
The bulk of this evidence was provided by the 19 countries with good quality data, namely 58.9 million persons followed through 336 million years of exposure-to-risk resulting in 44.5 million deaths. The data are given by country in Annex Table 1.
Updated by V. Castanova, 1 March 1999