[semimojo]

It sounds like you have no idea what a multivariate analysis is about. Please note that this is not my problem to solve for you.

You're the one calculating the effect of the exemption/credit.

What other factors did you include in your multivariate analysis that leads you to believe a net $10/month is going to lead to an increase in the fertility rate?

Or didn't you try to model the real world either?

[NobleFree]

What other factors did you include in your multivariate analysis

It's the authors' analysis. For the other factors, read the link - move your lips if it helps.