I am building a model to forecast unemployment using GDP, the CPI index and the industrial production index (INDPRO) as covariates. Since I am looking to use stationary time series, I gathered the percentage changes of each of these quantities such that the model now looks something like this:
%Unemployment = f(%GDP, %CPI, %INDPRO)
Is this an econometrically-sound model specification? Or should I use other data transformations since CPI and INDPRO are already expressed in percentages?