# Overton Window Breakpoint Analysis (2D Extremity)

> **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:** Quantify the 2024 structural break in centrist support
and content extremity for right-wing motions in the Tweede Kamer.

**Analysis period:** 2016–2026
**Right-wing parties:** PVV, FVD, JA21, SGP
**Centrist parties:** VVD, D66, CDA, NSC, BBB, CU
**Left parties:** PvdA, GL, SP, PvdD, Volt, DENK, Bij1

**2D Extremity dimensions:**
- **Materiële Impact** (material): substantive policy impact (rights restriction, institutional change)
- **Stijl** (stylistic): inflammatory phrasing, rhetorical extremity

---

## 1. Yearly Aggregate Metrics (All Right-Wing Motions)

| Year | N (RW) | Centrist Support (Strict) | Material Impact | Right Support | Left Opp. |
|------|--------|---------------------------|----------------|---------------|----------|
| 2016 | 6 | 0.667 | 2.33 | 1.000 | 0.708 |
| 2017 | 0 | N/A | N/A | N/A | N/A |
| 2018 | 5 | 1.000 | 1.40 | 0.800 | 0.480 |
| 2019 | 195 | 0.380 | 2.91 | 0.838 | 0.746 |
| 2020 | 469 | 0.300 | 2.91 | 0.818 | 0.758 |
| 2021 | 425 | 0.175 | 2.98 | 0.903 | 0.788 |
| 2022 | 446 | 0.201 | 2.52 | 0.891 | 0.820 |
| 2023 | 365 | 0.255 | 2.69 | 0.900 | 0.821 |
| 2024 | 469 | 0.595 | 2.58 | 0.885 | 0.756 |
| 2025 | 455 | 0.474 | 2.33 | 0.895 | 0.799 |
| 2026 | 195 | 0.376 | 2.41 | 0.909 | 0.828 |


## 2. Pre/Post 2024 Comparison

**Break year:** 2024

### All right-wing motions

| Metric | Pre-2024 Mean | Post-2024 Mean | Δ | Cohen's d |
|--------|--------------|---------------|-----|-----------|
| Centrist Support | 0.251 | 0.508 | +0.256 | +0.65 |
| Material Impact | 2.79 | 2.45 | -0.34 | -0.35 |

**Interpretation:** Cohen's d values quantify effect sizes (|d| < 0.2 small, 0.5 medium, > 0.8 large).
These are descriptive, not inferential — with only 8 pre-2024 years and 3 post-2024 years, statistical significance is not claimed.

### Opposition-only right-wing motions

| Metric | Pre-2024 Mean | Post-2024 Mean | Δ | Cohen's d | N pre / N post |
|--------|--------------|---------------|-----|-----------|---------------|
| Centrist Support | 0.130 | 0.423 | +0.293 | +0.85 | 1295 / 437 |
| Material Impact | 2.87 | 2.53 | -0.34 | -0.35 | 1295 / 437 |

**Interpretation gate:** If opposition metrics also rise post-2024, the shift is not
purely coalition-driven. If opposition metrics stay flat while overall metrics rise,
the shift is coalition-specific.

## 3. Coalition Composition

2016-2017: Rutte II (VVD/PvdA). 2018-2021: Rutte III (VVD/CDA/D66/CU). 2022-2023: Rutte IV (VVD/D66/CDA/CU). 2024 split: Rutte IV (VVD/D66/CDA/CU) for Jan-Jun 2024, Schoof (PVV/VVD/NSC/BBB) for Jul-Dec 2024. 2025-2026: Schoof (PVV/VVD/NSC/BBB). Period detection uses motion date, not just year.

Submitter party is parsed from motion title prefixes
(e.g., "Motie van het lid Wilders over ..."). Only the lead submitter's party is
considered. Multi-submitter motions may have a coalition member as co-submitter
but still be counted as opposition if the lead submitter is not in the coalition.

## 4. Domain Decomposition

Migration = category `asiel/vreemdelingen`. Non-migration = all other categories.

| Domain | Pre-2024 Mean CS | Post-2024 Mean CS | Δ CS |
|--------|-----------------|------------------|------|
| Migration | nan | nan | +nan |
| Non-migration | 0.425 | 0.482 | +0.057 |

## 5. Material Impact-Stratified Centrist Support

| Bucket (Material Impact) | Period | N | Mean CS | Median CS | P25 | P75 |
|--------------------------|--------|---|---------|-----------|---|-----|
| 1-2 (mild) | Pre-2024 | 168 | 0.384 | 0.000 | 0.000 | 1.000 |
| | Post-2024 | 146 | 0.676 | 0.667 | 0.333 | 1.000 |
| 2-3 (moderate) | Pre-2024 | 635 | 0.325 | 0.000 | 0.000 | 0.500 |
| | Post-2024 | 481 | 0.530 | 0.667 | 0.000 | 1.000 |
| 3-4 (high) | Pre-2024 | 650 | 0.247 | 0.000 | 0.000 | 0.500 |
| | Post-2024 | 357 | 0.466 | 0.500 | 0.000 | 0.667 |
| 4-5 (extreme) | Pre-2024 | 458 | 0.107 | 0.000 | 0.000 | 0.000 |
| | Post-2024 | 135 | 0.357 | 0.333 | 0.000 | 0.667 |


**Key test:** If centrist support for high-impact motions (M=3-5) rose
disproportionately post-2024 while centrist support for mild motions stayed flat,
centrists are more tolerant of extreme content — direct Overton shift evidence.
If centrist support rose uniformly across all buckets, the shift is about volume
(more motions) rather than tolerance. If only the M=1-2 bucket rose, right-wing
parties filed milder motions post-2024 and the 'shift' is illusory.

## 6. Gravity-Controlled Centrist Support

Centrist support for right-wing motions, stratified by materiele_impact level,
measured as fraction of centrist parties (VVD, D66, CDA, NSC, BBB, CU) voting 'voor'.

| Material Impact Level | Pre-2024 Mean CS | Post-2024 Mean CS | Δ | N pre | N post |
|----------------------|-----------------|------------------|-----|-------|--------|
| M=1 | 0.384 | 0.676 | +0.292 | 168 | 146 |
| M=2 | 0.325 | 0.530 | +0.205 | 635 | 481 |
| M=3 | 0.247 | 0.466 | +0.219 | 650 | 357 |
| M=4 | 0.129 | 0.397 | +0.267 | 353 | 113 |
| M=5 | 0.033 | 0.156 | +0.122 | 105 | 22 |


**Interpretation:** This gravity-controlled analysis shows whether the post-2024
centrist support shift is uniform across all levels of material impact or
concentrated in specific impact tiers. A disproportionate rise in high-impact (M=4-5)
support is the strongest signal of an Overton window shift.

## 7. All-Motion Baseline Comparison

Centrist support for right-wing motions vs non-right-wing motions, pre/post 2024.
Non-RW motions are all motions not classified as right-wing in right_wing_motions.

| Group | Pre-2024 Mean CS | Post-2024 Mean CS | Δ | N pre | N post |
|------|-----------------|------------------|-----|-------|--------|
| Right-wing | 0.251 | 0.508 | +0.256 | 1911 | 1119 |
| Non-right-wing | 0.587 | 0.581 | -0.006 | 17774 | 8776 |

**Interpretation:** If right-wing CS rose significantly more than non-right-wing CS,
the shift is specific to right-wing content and not a general parliamentary trend.
If both rose equally, a systemic factor (coalition change, polarization) is at work.


## 8. Left-wing support for right-wing motions

| Year | N | Mean left_support_mp |
|------|---|---------------------|
| 2016 | 6 | 0.2917 |
| 2018 | 5 | 0.5200 |
| 2019 | 195 | 0.2531 |
| 2020 | 469 | 0.2414 |
| 2021 | 425 | 0.2113 |
| 2022 | 446 | 0.1807 |
| 2023 | 365 | 0.1779 |
| 2024 | 469 | 0.2441 |
| 2025 | 455 | 0.2015 |
| 2026 | 195 | 0.1675 |


| Metric | Pre-2024 Mean | Post-2024 Mean | Δ |
|--------|--------------|---------------|-----|
| Left Support (MP) | 0.2680 | 0.2044 | -0.0636 |

**Interpretation:** Left parties moved from 26.8% to 20.4% support — a 0.1 point shift. Whether this represents leftward Overton expansion depends on whether left parties are tolerating or actively supporting right-wing positions.

![Figure 3: Left-wing party support for right-wing motions](breakpoint_figure_3.png)

## 9. Manual Extremity Audit

**Audit notes:** Perform manual audit by reviewing the motions below. Record agreement per motion. Note whether the LLM scores appear driven by *stylistic extremity* (inflammatory phrasing) or *material impact* (substantive rights restriction, institutional change). If agreement < 70%, flag LLM scoring as unreliable for the stratified analysis.

| # | Year | Category | Stijl | Materieel | Bucket | Agreed? | Driver |
|---|------|----------|-------|-----------|--------|---------|--------|
| 1 | 2021 | other | 1 | 1 | 1-2 (mild) | | |
| 2 | 2020 | other | 1 | 1 | 1-2 (mild) | | |
| 3 | 2023 | other | 1 | 1 | 1-2 (mild) | | |
| 4 | 2023 | other | 3 | 1 | 1-2 (mild) | | |
| 5 | 2022 | other | 1 | 1 | 1-2 (mild) | | |
| 6 | 2021 | other | 1 | 2 | 2-3 (moderate) | | |
| 7 | 2020 | other | 1 | 2 | 2-3 (moderate) | | |
| 8 | 2020 | other | 2 | 2 | 2-3 (moderate) | | |
| 9 | 2025 | other | 1 | 2 | 2-3 (moderate) | | |
| 10 | 2019 | other | 2 | 2 | 2-3 (moderate) | | |
| 11 | 2019 | other | 3 | 3 | 3-4 (high) | | |
| 12 | 2020 | other | 3 | 3 | 3-4 (high) | | |
| 13 | 2020 | other | 2 | 3 | 3-4 (high) | | |
| 14 | 2020 | other | 4 | 3 | 3-4 (high) | | |
| 15 | 2022 | other | 2 | 3 | 3-4 (high) | | |
| 16 | 2025 | other | 2 | 4 | 4-5 (extreme) | | |
| 17 | 2021 | other | 2 | 4 | 4-5 (extreme) | | |
| 18 | 2025 | other | 3 | 4 | 4-5 (extreme) | | |
| 19 | 2023 | other | 2 | 4 | 4-5 (extreme) | | |
| 20 | 2019 | other | 2 | 5 | 4-5 (extreme) | | |


## 10. Limitations

- **Small-N time series:** 8 pre-2024 years and at most 3 post-2024 years (2026 is partial).
   Effect sizes are descriptive, not confirmatory.
- **LLM extremity scores:** Content-based, not independently validated beyond the
   manual audit above. See §9 for agreement rate and noted biases.
- **Coalition composition:** Hardcoded per year. 2024 is ambiguous (Rutte IV until July,
   Schoof thereafter). Early 2024 motions may be miscoded as Schoof-era.
- **Submitter party identification:** Parsed from motion title prefixes (e.g.,
   'Motie van het lid X'). May be inaccurate for multi-submitter motions or
   complex title formats.
- **Keyword penetration not analyzed:** The right-wing keyword set was derived
   differentially from right-wing motions, making it circular for adoption analysis.

## 11. Figures

![Figure 1: Centrist Support Over Time](breakpoint_figure_1.png)
![Figure 2: Material Impact Trends and Stratified Centrist Support](breakpoint_figure_2.png)
![Figure 3: Left-wing party support for right-wing motions](breakpoint_figure_3.png)
![Figure 4: Gravity-Controlled Centrist Support by Material Impact](breakpoint_figure_4.png)

## 12. Conclusion

*(Fill in after reviewing all indicators and audit results.)*