Who believes in the growth number?

I am taking an informal survey (email me) on the GDP number -- do you believe it? If so, do you believe that the tax cut is the reason or do you have a different theory? If not, what do you think it really was? 7.2% !? Here is what I want to know -- how do home refinancings figure into this number? Could it be that the real reason that GDP seems so high is low interest rates?