Economics of Ageing

Demographic and economic research in population ageing may apply quite different definitions of ageing.A typical demographic definition like that found in Billeter (1954) characterizes the age structure of a population by <math display='block'> <mrow> <msub> <mi>D</mi> <mn>1</mn> </msub> <mo>:</mo><mo>=</mo><mfrac> <mrow> <msub> <mi>P</mi> <mrow> <mn>0</mn><mo>,</mo><mtext>&#x2009;</mtext><mn>14</mn> </mrow> </msub> <mo>&#x2212;</mo><msub> <mi>P</mi> <mrow> <mn>50</mn><mo>,</mo><mtext>&#x2009;</mtext><mo>+</mo> </mrow> </msub> </mrow> <mrow> <msub> <mi>P</mi> <mrow> <mn>15</mn><mo>,</mo><mtext>&#x2009;</mtext><mn>49</mn> </mrow> </msub> </mrow> </mfrac> </mrow> </math>$${D_1}: = \frac{{{P_{0,\,14}} - {P_{50,\, + }}}}{{{P_{15,\,49}}}}$$ where P_{a, b} is the number of people between a and b years of age and P_a,+ is the number of people aged a years and older. This measure differentiates age groups according to their reproductive abilities. The future development of the population is expressed in this measure by subtracting the old non-productive from the young non-productive part of the population. If the percentage of people over 50 is high, then D ₁ is negative. An aged population is therefore characterized by a high negative value of D₁, and the demographic problems become worse if this negative value increases in absolute terms (ageing).