Suppose that you want to estimate whether increasing the pension people receive affects the age at which they retire. By

[answerhappygod]

Suppose that you want to estimate whether increasing the pension
people receive affects the age at
which they retire. By a law passed in the past, people born before
1950 are eligible for higher pensions
than people born later. When carrying out a
regression-discontinuity estimation, what would be your
running variable?

a) The age at which people retire
b) Year of birth
c) The amount of pension
d) Whether the pension people receive has increased