Why does the Washington Working Families Tax Credit increase the income share held by the top 1%?

[MaxGhenis]

Need to investigate this before promoting the Washington launch:

From a reform that introduces the WFTC against a baseline that repeals it:
https://policyengine.org/us/population-impact?wa_wftc_max_amount_0_rate=300&wa_wftc_max_amount_1_rate=600&wa_wftc_max_amount_2_rate=900&wa_wftc_max_amount_3_rate=1200&baseline_wa_wftc_max_amount_0_rate=0&baseline_wa_wftc_max_amount_1_rate=0&baseline_wa_wftc_max_amount_2_rate=0&baseline_wa_wftc_max_amount_3_rate=0&baseline_state_specific=WA

[MaxGhenis]

This could be part of it: some people come out behind from the WFTC's introduction. This shouldn't happen.

[MaxGhenis]

Zeroing out the minimum amount avoids anyone coming out behind, but the top 1% share still rises 2.7%.

[MaxGhenis]

Seems to be the legit result of a single record in the CPS: this notebook shows that Washington's fourth-highest-equivalized-income SPM unit (which is in the top 1%) has two tax units. One is eligible for $900 in the WFTC. I expect this is a statistical fluke that will go away when we reweight the full CPS.