# Motion Semantic Drift Analysis Report

**Windows analyzed:** 2016, 2017, 2018, 2019, 2022, 2023, 2024, 2025, 2026
**Top N motions per axis:** 20

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## Summary

- **Stable axes:** [1, 2, 3, 4, 5, 7, 8, 9, 10]
- **Axes with inflection points:** 1
- **Parties with cross-ideological voting:** 0

## Axis Stability

![Axis Stability Heatmap](axis_stability.png)

**Stable axes (similarity > 0.7):** [1, 2, 3, 4, 5, 7, 8, 9, 10]
**Reordered axes:** [6]
**Unstable axes:** []

## Semantic Drift

![Semantic Drift Timeline](semantic_drift.png)

### Axis 8 Inflection Points

- **2016 → 2017**: drift=1.7467 (median=0.4850)
- **2017 → 2018**: drift=1.7470 (median=0.4850)

## Party Voting Analysis

**Parties tracked:** 47

![Party Trajectories](party_trajectories.png)

No cross-ideological voting detected.

## Overtone Shift

Overtone shift measures how the semantic content of motions on each axis changes over time, even when party ordering stays the same.

### Axis 1

- **Average shift:** 1.4680
- **Max shift:** 1.9709
- **Inflection points:** 0

### Axis 2

- **Average shift:** 1.4220
- **Max shift:** 1.7869
- **Inflection points:** 0

### Axis 3

- **Average shift:** 1.3830
- **Max shift:** 1.8293
- **Inflection points:** 0

### Axis 4

- **Average shift:** 1.3946
- **Max shift:** 1.8857
- **Inflection points:** 0

### Axis 5

- **Average shift:** 1.4333
- **Max shift:** 1.9253
- **Inflection points:** 0

### Axis 7

- **Average shift:** 1.3068
- **Max shift:** 1.8408
- **Inflection points:** 0

### Axis 8

- **Average shift:** 1.3022
- **Max shift:** 1.8897
- **Inflection points:** 0

### Axis 9

- **Average shift:** 1.3751
- **Max shift:** 1.9262
- **Inflection points:** 0

### Axis 10

- **Average shift:** 1.2993
- **Max shift:** 1.7220
- **Inflection points:** 0

## Methodology

- **Axis stability:** Ridge regression weights (SVD_score ~ fused_embedding) per axis per window, compared via max(cosine similarity, Jaccard top-100 dimensions)
- **Overtone shift:** Semantic gravity (weighted mean fused embedding) per axis per window, tracked via cosine distance between consecutive windows
- **Semantic drift:** Cosine distance between fused embedding centroids of top-N motions per axis
- **Inflection points:** Drift/shift rate exceeding 2× median rate
- **Cross-ideological voting:** Parties voting 'voor' on motions where canonical opposite-wing parties have high loadings

- **Semantic drift:** Cosine distance between fused embedding centroids of top-N motions per axis
- **Inflection points:** Drift rate exceeding 2× median drift rate
- **Cross-ideological voting:** Parties voting 'voor' on motions where canonical opposite-wing parties have high loadings