Hi all!

I am an econ student finishing my bachelor thesis and I have an econometrics section coming up. I have to discuss results obtained from computations.
My objective vould be to prove a causality link between shadow economy and cash in circulation (cash causes more shadow economy).
I run first a IV 2SLS regression as
Shad = Cval (Opp as instrument).

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And this is the result. Before I continue, I do not recall much and textbooxs confused my ideas even more.
My R-squared is somewhat high but f test and p values are way too high. So i tried a 3SLS reg

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Which seems better but honestly I am not sure how to interpret it.
Any help would be much appreciated.

Thanks