ABSTRACT
This chapter examines the ways in which the meaning of middle age has changed over time to provide a working definition of middle age and to use this definition to calculate the number, and proportion, of the population that should be described as middle-aged at various points over the past hundred years. It will be argued that the meaning of middle age has changed in several significant respects, and that the number, and proportion, of the population that should be described as middle-aged has grown substantially since the beginning of the twentieth century. It is proposed therefore that the working definition of middle age to be used will be chronologically based. By the 1990s, Armed with this working definition of middle age, it is possible to provide estimates of the number, and proportion, of the population that should be described as middle-aged at ten-yearly intervals since the beginning of the twentieth century.
