Right with those parameters, so if you just look at the er coefficional income, if we estimate the coefficional income to be nought point five right, over the entire sample, the then subsequently find out if that coefficient varies from year to year from minus six plus ten, right, having a one point estimate, right, er oh that coefficient is not going to be particularly useful to us, we want to know er whether our coefficients remain reasonably constant throughout our sample period, particularly if we're using this er equation to make out of sample predictions, right.