Add repeal state dependent exemptions analysis

us/state_dependent_exemptions/README.md

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+# Repeal State Dependent Exemptions
+
+Reform parameter: `gov.contrib.repeal_state_dependent_exemptions.in_effect`
+
+This reform repeals all state-level dependent exemptions, credits, and deductions that are specifically tied to the number of dependents in a tax unit. Updated formulas replace `tax_unit_size` or `exemptions_count` (which include dependents) with `head_spouse_count` (which excludes them).
+
+## Microsimulation results
+
+Dataset: `enhanced_cps_2024` | Period: 2024
+
+| Metric | Value |
+|---|---|
+| Total state tax revenue increase | $5.87B |
+| Total household net income decrease | -$5.87B |
+| Benefit spending change | $0 |
+| Households affected | 20.7M (14.4%) |
+| States affected | 34 of 51 |
+
+Full state-by-state results are in `state_impacts_detailed.csv`.
+
+### Top 10 states by net income impact
+
+| State | Net income impact | State tax revenue change | Avg change/HH | % HH affected |
+|---|---|---|---|---|
+| CA | -$2.43B | +$2.43B | -$163 | 23.1% |
+| MI | -$479M | +$479M | -$107 | 24.7% |
+| MN | -$433M | +$433M | -$165 | 29.2% |
+| IL | -$350M | +$350M | -$60 | 26.9% |
+| GA | -$255M | +$255M | -$52 | 20.7% |
+| NY | -$245M | +$245M | -$29 | 24.0% |
+| SC | -$195M | +$195M | -$82 | 13.4% |
+| OH | -$157M | +$157M | -$31 | 23.4% |
+| MD | -$140M | +$140M | -$56 | 21.6% |
+| NJ | -$117M | +$117M | -$30 | 33.8% |
+
+## Variables modified by the reform
+
+### Neutralized variables (set to zero)
+
+These are dependent-specific variables that are entirely zeroed out.
+
+| Variable | State | Description |
+|---|---|---|
+| `al_dependent_exemption` | AL | Alabama dependent exemption |
+| `il_dependent_exemption` | IL | Illinois dependent exemption |
+| `la_dependents_exemption` | LA | Louisiana dependents exemption |
+| `mn_exemptions` | MN | Minnesota exemptions (includes dependents) |
+| `ms_dependents_exemption` | MS | Mississippi dependents exemption |
+| `nj_dependents_exemption` | NJ | New Jersey dependents exemption |
+| `ny_exemptions` | NY | New York exemptions (includes dependents) |
+| `sc_dependent_exemption` | SC | South Carolina dependent exemption |
+| `ut_personal_exemption` | UT | Utah personal exemption (includes dependents) |
+| `nc_child_deduction` | NC | North Carolina child deduction |
+| `nm_deduction_for_certain_dependents` | NM | New Mexico deduction for certain dependents |
+| `mt_dependent_exemptions_person` | MT | Montana dependent exemptions per person (no effect in 2024; MT eliminated exemptions) |
+| `az_dependent_tax_credit` | AZ | Arizona dependent tax credit |
+| `ar_personal_credit_dependent` | AR | Arkansas personal credit for dependents |
+| `id_ctc` | ID | Idaho child tax credit |
+| `me_dependent_exemption_credit` | ME | Maine dependent exemption credit |
+
+### Updated variables (formula changed to exclude dependents)
+
+These variables originally used `tax_unit_size`, `exemptions_count`, or `tax_unit_dependents` to include dependents. The reform replaces those with `head_spouse_count` or removes the dependent component.
+
+| Variable | State | Original pattern | Reform change |
+|---|---|---|---|
+| `hi_regular_exemptions` | HI | `exemptions_count` (all members) | Uses `head_spouse_count` (head + spouse only) |
+| `md_total_personal_exemptions` | MD | `tax_unit_size` (all members) | Uses `head_spouse_count` |
+| `mi_personal_exemptions` | MI | `exemptions_count` (all members) | Uses `head_spouse_count` + stillborn children |
+| `ne_exemptions` | NE | `exemptions_count` (all members) | Uses `head_spouse_count` |
+| `oh_personal_exemptions_eligible_person` | OH | Eligible if head/spouse OR dependent | Eligible only if head/spouse |
+| `ok_count_exemptions` | OK | Included dependent exemptions in count | Head + spouse exemptions only |
+| `ri_exemptions` | RI | `exemptions_count` (all members) | Uses `head_spouse_count` |
+| `vt_personal_exemptions` | VT | Counted dependents in total | Head + spouse only |
+| `va_personal_exemption_person` | VA | Applied to all members | Head + spouse only |
+| `wv_personal_exemption` | WV | `tax_unit_size` (all members) | Uses `head_spouse_count` |
+| `ca_exemptions` | CA | Included dependent credit count | Personal + aged/blind only |
+| `ga_exemptions` | GA | `personal + dependent` exemptions | Personal exemptions only |
+| `in_base_exemptions` | IN | `exemptions_count` (all members) | Uses `head_spouse_count` |
+| `ks_exemptions` | KS | Included dependent amount (2024: `by_filing_status.dependent * dependents`) | Removes dependent amount; keeps base + HOH + veteran amounts |
+| `ma_income_tax_exemption_threshold` | MA | Threshold included dependent count | Threshold for head/spouse only |
+| `wi_base_exemption` | WI | `exemptions_count` (all members) | Uses `head_spouse_count` |
+| `ia_exemption_credit` | IA | Counted dependents in exemption credit | Head/spouse + elderly/blind only |
+| `de_personal_credit` | DE | `exemptions_count` (all members) | Uses `head_spouse_count` |
+| `ky_family_size_tax_credit_rate` | KY | `tax_unit_size` for poverty index | Uses `head_spouse_count` for poverty index |
+| `ok_child_care_child_tax_credit` | OK | Greater of 20% CDCC potential or 5% CTC | 20% of CDCC only (removes CTC component) |
+
+## Out-of-scope variables
+
+The following variables reference dependents but are **not** dependent exemptions. They are separate tax programs (credits, rebates, tax rate selection, EITC adjustments) and are intentionally excluded from this reform.
+
+| Variable | State | Type | Reason excluded |
+|---|---|---|---|
+| `ct_child_tax_rebate` | CT | Rebate | Per-child cash rebate, not an exemption |
+| `ct_property_tax_credit_eligible` | CT | Credit eligibility | Eligibility check (dependents OR elderly) |
+| `il_income_tax_rebate` | IL | Rebate | Base + per-dependent rebate amount |
+| `ar_low_income_tax_joint` | AR | Tax rate selection | Selects low-income tax table by dependent count |
+| `az_family_tax_credit_eligible` | AZ | Credit eligibility | Income limit varies by dependent count |
+| `vt_eitc` | VT | EITC adjustment | Match rate varies by child count |
+| `ks_fstc` | KS | Food sales tax credit | Credit per exemption for food sales tax |
+| `ma_part_b_taxable_income_exemption` | MA | Part B exemption | Includes dependent component but is a broader exemption |
+| `ma_scb_total_income` | MA | Income calculation | Re-adds exemptions for Senior Circuit Breaker |
+| `hi_disabled_exemptions` | HI | Disabled filer exemption | Dependent exemption only when head/spouse is disabled |
+| `wi_homestead_income` | WI | Credit income | Reduces income by dependent exemption for homestead credit |
+
+## Methodology
+
+The analysis follows the exact same pattern as the PolicyEngine API (`budget.py` / `compare.py`):
+
+- `sim.calc()` returns `MicroSeries` with embedded survey weights
+- `.sum()` gives weighted population totals (no manual weight multiplication)
+- `.count()` gives total household count (sum of weights)
+- `household_tax`, `household_state_income_tax`, `household_benefits`, `household_net_income` match the API's tracked variables
+- State-level groupby uses `MicroSeries.groupby(state_code).sum()` for weighted aggregation
+
+## Files
+
+- `repeal_state_dependent_exemptions.py` - Analysis script
+- `state_impacts_detailed.csv` - Full state-by-state results
+- `README.md` - This documentation