title: Is multicollinearity an issue if I do not intend to interprest the coefficient if the varaible?
body: <p>I am creating a model to check whether the threat of entry affects prices in the same way in two different samples. I will therefore only interpret the coefficients of the time dummies, which will hopefully be significant. In the model I will also add other parameters to control for systematic differences in characteristics between the two groups, to make them more comparable. Therefore, I do not care about whether these coefficients are significant, they just have to be controls. Do I have to care about multicollinearity among those controls? or even if the information they carry is for the most part similar (corr.coef 0.77),  the extra is still worth keeping to better isolate the effect expressed by the time dummies?</p>