Calibrate to taxable returns

[MaxGhenis]

SOI publications report All returns and Taxable returns separately. Per #4283, we may want to focus calibration on taxable returns, given the various non-policy reasons people may file non-taxable returns.

SOI publication 1304 defines a taxable return as follows:

Taxable and Nontaxable Returns
The taxable and nontaxable classification of a return for this report is determined by the presence of 'total income tax.' Some returns classified as 'nontaxable' may have had a liability for other taxes, such as excess advance premium tax credit (APTC) repayment, self-employment tax, uncollected employee Social Security and Medicare tax on tips, tax from recomputing prior-year investment credit, penalty taxes on individual retirement accounts, section 72 penalty taxes, household employment taxes, Additional Medicare Taxes, or golden parachute payments. These taxes, however, were disregarded for the purposes of this classification, since four of the above taxes were considered Social Security (rather than income) taxes, and the remaining ones either were based on prior year’s income or were penalty taxes. The APTC repayment was not an income tax but a repayment of money previously advanced to taxpayers for paying for health insurance purchased on a health care exchange. Net Investment Income Tax from Form 8960 was added to income tax after credits to create income tax. For this report, the earned income credit, additional child credit, American opportunity credit, premium tax credit, regulated investment company credit, and health coverage credit are treated first as an amount used to offset income tax before credits. Since they were refundable, they were subtracted from income tax (for the statistics) after reduction by all other statutory credits. As a result, some returns became nontaxable strictly because of the refundable credits when the refundable credits equaled or exceeded income tax before credits reduced by any other credits. It should be noted that classification as taxable or nontaxable was based on each return as it was filed and does not reflect any changes resulting from audit or other enforcement activities. (See also 'Total Income Tax.')

I think this would be income_tax > 0 in our model, as that does not include self-employment and payroll taxes (including the Additional Medicare Tax).