Which variable would be most useful in determining the number of people eligible for retirement benefits in a certain year?

The most useful variable in determining the number of people eligible for retirement benefits in a certain year would be the age distribution of the population. Specifically, the proportion of individuals aged 65 and older is critical, as this age group typically qualifies for retirement benefits. Additionally, factors such as workforce participation rates and changes in retirement age policies may also influence eligibility. Analyzing these Demographics can provide a clearer picture of potential beneficiaries.