# Motion Success Correlation Analysis

> **Part of the Overton Window Analysis.** See the [synthesis report](overton_window_synthesis.md) for the integrated narrative, or the [interactive article](overton_window.qmd) for the full story with charts.

**Goal:** Test whether motions with high centrist support actually passed at higher rates,
validating that centrist support translates to legislative success.

**Analysis period:** 2016–2026
**Total right-wing motions:** 3030
**Motions with determinable outcome:** 3030
**Motions passed:** 2938 (97.0%)
**Government motions:** 620  ·  **Opposition motions:** 1700  ·  **Unknown type:** 710

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## 1. Pass Rate by Centrist Support Quartile

Centrist support (strict) is the fraction of centrist parties that voted 'voor'.
Quartile bins are: [0-0.25], (0.25-0.50], (0.50-0.75], (0.75-1.0].

| Stratum | Q1 [0.00–0.25] | Q2 (0.25–0.50] | Q3 (0.50–0.75] | Q4 (0.75–1.00] | N total | Trend χ² | p-value |
|---------|--------------|--------------|--------------|--------------|---------|-----------|---------|
| all | 96.3% (n=1607) | 94.6% (n=542) | 99.6% (n=230) | 99.5% (n=651) | 3030 | 18.92 | <0.001 |
| pre-2024 | 96.2% (n=1247) | 91.9% (n=357) | 90.0% (n=10) | 99.3% (n=297) | 1911 | 2.69 | 0.101 |
| post-2024 | 96.7% (n=360) | 100.0% (n=185) | 100.0% (n=220) | 99.7% (n=354) | 1119 | 14.05 | <0.001 |
| government | 98.1% (n=161) | 96.4% (n=166) | 100.0% (n=82) | 99.5% (n=211) | 620 | 3.00 | 0.083 |
| opposition | 96.1% (n=1201) | 93.0% (n=228) | 98.9% (n=89) | 99.5% (n=182) | 1700 | 3.82 | 0.051 |

**Cochran-Armitage trend test:** Tests for a monotonic trend in pass rates across
ordered quartile bins. A significant result (p < 0.05) indicates that pass rates
increase or decrease systematically with centrist support level.

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## 2. Success Premium

The "success premium" is the difference in pass_rate between the highest centrist
support quartile (Q4) and the lowest (Q1): pass_rate(Q4) - pass_rate(Q1).

| Stratum | Q1 Pass Rate | Q4 Pass Rate | Premium |
|---------|-------------|-------------|---------|
| all | 96.3% | 99.5% | +3.2% |
| pre-2024 | 96.2% | 99.3% | +3.1% |
| post-2024 | 96.7% | 99.7% | +3.1% |
| government | 98.1% | 99.5% | +1.4% |
| opposition | 96.1% | 99.5% | +3.4% |

Positive premium → higher centrist support correlates with higher pass rate.
Negative premium → higher centrist support correlates with lower pass rate.

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## 3. Period Stratification (Pre vs Post-2024)

Pre-2024: 2016–2023 (Rutte cabinets II–IV).
Post-2024: 2024–2026 (Schoof cabinet, PVV in coalition).

The post-2024 period has far more right-wing motions (volume surge).
If the success premium differs between periods, the structural break
affected not just centrist willingness to support but also motion outcomes.

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## 4. Government vs Opposition Control

Government motions come from coalition party members and generally have higher
baseline pass rates. Opposition motions are the true test: if high centrist support
predicts passage for opposition motions, centrist backing is decisive.

Motion type is determined by parsing the lead submitter from the title prefix
(e.g., 'Motie van het lid Wilders over ...').

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## 5. Interpretation

The Cochran-Armitage trend test is significant (χ²=18.92, p=0.000), indicating a positive monotonic relationship between centrist support and pass rate. The success premium is +3.2%.

For opposition motions specifically, the trend test is not significant (χ²=3.82, p=0.051).

### Period Comparison
- **pre-2024** (n=1911): χ²=2.69, p=0.101, premium=+3.1%
- **post-2024** (n=1119): χ²=14.05, p=0.000, premium=+3.1%

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## 6. Limitations

- **Ceiling effect:** Dutch parliamentary motions pass at very high rates (>95%),
  leaving little variance to detect correlation with centrist support.
- **Undetermined outcomes:** Some motions had equal votes or no voting data,
  reducing sample size (excluded from pass rate calculation).
- **Submitter parsing:** Lead submitter party identification from title prefixes
  may misclassify some multi-submitter motions.
- **Coalition coding:** 2024 is ambiguous (Rutte IV until July, Schoof thereafter).
- **Causality direction:** Correlation does not imply causation. High centrist support
  could reflect motions that were already likely to pass (centrists voting with the
  majority), rather than centrist support causing passage.

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*Report generated by `analysis/right_wing/success_correlation.py`*