For the log-log model ln(Y)=β0+β1ln(X)+ϵ\ln(Y) = \beta_0 + \beta_1 \ln(X) + \epsilonln(Y)=β0+β1ln(X)+ϵ, how is the coefficient β1\beta_1β1 interpreted?
An elasticity: a 1% change in X leads to a \beta_1% change in Y.
A 1-unit change in X leads to a \beta_1-unit change in Y.
A 1-unit change in X leads to a \beta_1% change in Y.
A 1% change in X leads to a \beta_1-unit change in Y.