Elasticity is proportional change in population growth rate

resulting from a small change in a vital rate. Elasticities are

usually calculated for long-run population growth rates: dominant

eigenvalue of the projection matrix in a deterministic environment

or stochastic growth rate in the presence of environmental

variation. We derive elasticities of yearly growth rates, which

are time dependent, in varying environments. This is called

real-time elasticity. We show that moving averages of real-time

elasticities converge to long-run stochastic elasticity, thus

making a connection between short-term and long-term selection.

When there is no environmental variation real-time elasticities

reduce to transient elasticities. Our results explain why

transient elasticities differ from asymptotic ones and how this

difference depends on the demography of the species. We describe

applications of our results in life-history evolution and

conservation biology.