TAXSIM-35 Validation, "a" files

[jdebacker]

This PR adds the "expected" files for differences between Tax-Calculator and TAXSIM-35 for the "a" validation sample. This is the sample with the simplest returns.

We are looking for the differences between each to diff economically insignificant or explain through some difference in the two models.

The following years' files will be added here (and checked off below when differences are explained/resolved):

• 2017
• 2018
• 2019
  • 2 obs with diffs for iitax of $196 -- seems to come from eitc diff (note, the max diff in the eitc comes from same record as max offs in mtr)
• 2020
  • 133 obs with differing rrc (this may be due to TAXSIM-35 not counting the Jan/March 2021 RRC amounts in 2020)
  • 9 obs with differing eitc, up to 75.82
  • 62 obs with differing mtr_inctax
• 2021
  • c11070 diff for 502 records - up to 12500
  • non_refundable_child_odep_credit diff for 172 obs - up to 4000 (does this relate rrc for jan 2021??)
  • 40 recs with diffs in mtr_inctax up to 80
  • 104 recs with diff iitax, up to 2500

cc @bodiyang

[bodiyang]

the 2019 'a' set: Tax Calculator is correct
2 obs with diffs for iitax of $196 -- seems to come from eitc diff

• record 348: $0.01 diff in iitax ~ can be ignored (diff might come from rounding rules)

• record 905: $192 diff in iitax ~ $192 diff in eitc
  Tax filler's age is 19, not eligible for EITC (childless tax filler's age must be between 25~65 to be eligible for EITC)
  EITC amount: Tax-Calculator $0; Taxsim $196
  Tax-Calculator should be right; Taxsim does not consider the EITC age cap

[bodiyang]

the 2020 'a' set:

records iitax diff mainly come from:

• recovery rebate credit
  I have manually calculated the records with differences and Tax-Calculator should be correct. The reasons Taxsim showing different results vary
  ~ examples including: not counting qualifying children (id 7); taxsim do not differentiate single/head of household filing status (id 31); taxsim not counting EIP2 (if 33); taxsim counts wrong number of child (id 59)

• eitc
  The EITC_ps_MarriedJ for the year 2020 was incorrect in Tax-Calculator, which causing the eitc differences.
  This is fixed in the PR 2699

• mtr_inctax

[bodiyang]

the 2021 'a' set:

• For year 2021, Child tax credit is categorized as nonrefundable child tax credit. So c11070 as the refunded Child tax credit is count as zero in Tax-Calculator. Taxsim35 calculates the amount of Child tax credit (it does not differentiate refundable vs nonrefundable credit)

[jdebacker]

@bodiyang Thanks for documenting these known diffs in this issue. To keep track of these long-term, I've added a Differences_Explained.md file to this PR.

[bodiyang]

the 2021 'a' set showing no difference after the work to include other dependent credit into iitax calculation

@jdebacker I think this will conclude the validation work of 'a' set.

[jdebacker]

@bodiyang Thanks for your help. I believe this PR is ready for review and to merge following that.

[codecov]

Codecov Report

Merging #2698 (dd979a0) into master (b1eb957) will not change coverage.
Report is 1 commits behind head on master.
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