Code changes to model ARPA

[codykallen]

This implements the code changes necessary to model the tax changes in the American Rescue Plan Act of 2021, as described in issue #2571. This adds the following policy parameters and their associated logic:

• RRC_c, RRC_ps, RRC_pe: Parameters to implement the Recovery Rebate Credit (i.e. $1,400 payments)
• UI_em, UI_thd: Parameters to implement the exclusion of UI benefits from taxable income, up to $10,200 for those with AGI below $150,000.
• CDCC_ps2, CDCC_refundable: Parameters to implement changes to the CDCC.
• CTC_include17, CTC_refundable: Parameters to implement changes to the CTC.

In addition to these new policy parameters and the logic to implement them, I made the following further changes:

• Created policy parameters CDCC_frt and CDCC_prt, to replace their hardcoded values in the F2441 logic.
• Minor refactoring to the ChildDepTaxCredit function to make it easier to implement the CTC refundability. This refactoring removed some unnecessary code but does not change the underlying logic, so the results do not change.
• Fixed two whitespace errors flagged by pycodestyle.

The next steps for this PR are to add the reform file (in progress), and to add tests to provide coverage for the new code.

@MattHJensen, @martinholmer, @grantseiter, @MaxGhenis, @Thirdhuman, @ernietedeschi, @kpomerleau

[MattHJensen]

Enacter -> Enacted

[MattHJensen]

@codykallen, this is looking great to me upon initial review. I'll leave it open for others to take a look until this (Sunday) evening when I hope to merge and then release first thing tomorrow morning.

[codykallen]

Per the discussion with @kpomerleau in issue #2571, the newest commit changes how we calculate the number of 17-year-olds eligible for the CTC under ARPA. The previous logic raised the number of CTC-eligible children by 27.3 million in 2021, whereas the new logic raises it by 1.9 million, a much more reasonable result.

[rickecon]

It looks like the only test failing in this PR is in the Jupyter Book documentation tests. The error message looks like it has to do with Python 3.9. It says:

Specifications:

  - behresp -> python[version='3.6.*|>=3.6,<3.7.0a0|>=3.8,<3.9.0a0|>=3.7,<3.8.0a0']

Your python: python=3.9

The behresp model is installed in the Jupyter-Book-related GitHub Actions check_jupyterbook.yml, deploy_jupyterbook, and deploy_parameters_docs.yml.

The testing in these .yml docs specifies Python 3.9. However, the Behavioral-Responses repo from which the behresp package is created only tests in the .travis.yml up to Python 3.8 (see line 6). To fix this error, I recommend either of the following two options:

1. Update the Behavioral-Responses repository and resulting behresp package to run on Python 3.9, or
2. Change the Jupyter-Book-related GitHub Action tests in the Tax-Calculator repo (check_jupyterbook.yml, deploy_jupyterbook, deploy_parameters_docs.yml) to run on Python 3.8 rather than 3.9.

cc: @codykallen @MattHJensen @jdebacker

[MattHJensen]

@codykallen, thanks again for this big contribution. @jdebacker, @kpomerleau, and @rickecon, thanks for your help with the review process.

I am going to merge this now since the failing test should pass on master thanks to #2575. If it doesn't, we'll make sure it is passing before releasing.

[MattHJensen]

Sorry, @codykallen, I saw your latest commit right after merging, and I didn't let the tests run. They are running on master now. https://github.com/PSLmodels/Tax-Calculator/runs/2112290774

[MattHJensen]

Tests passed on master.