docs: caveat SVD spatial positions reflect voting patterns, not policy content

SVD axes capture agreement structure — centrists 'moving left' means
voting patterns diverged from right-wing, not that parties changed
ideology. 'Acceptance without conversion' is a behavioral claim.
Documented as best-practice learning.

docs/solutions/best-practices/svd-spatial-positions-voting-patterns-not-policy-content.md

@@ -0,0 +1,42 @@
+---
+module: analysis
+problem_type: best_practice
+date: 2026-05-25
+tags:
+  - svd
+  - overton-window
+  - voting-patterns
+  - policy-content
+  - spatial-analysis
+category: best-practices
+---
+
+# SVD Positions Reflect Voting Patterns, Not Policy Content
+
+## Context
+
+When analyzing political shifts with SVD/PCA party positions, it is tempting to interpret spatial movement as ideological change — "centrists moved left" sounds like centrist parties became more progressive. This interpretation is incorrect and dangerously misleading.
+
+## Guidance
+
+**SVD axes capture agreement structure, not policy positions.** A party's coordinate on an SVD axis reflects whom it votes with and against, not what policies it advocates. This was already documented in `svd-labels-voting-patterns-not-semantics.md` for axis labeling, but the same principle applies to spatial drift analysis.
+
+**What SVD movement actually means:**
+- Centrists moving left on an axis means centrist voting patterns became *more distinct* from right-wing voting patterns
+- It does NOT mean centrist parties adopted more left-wing policy positions
+- It does NOT mean the motions being voted on became more left-wing or right-wing in content
+
+**Why this matters for Overton window analysis:**
+- "Acceptance without conversion" (centrists vote more with right-wing while spatially diverging) is a claim about *voting behavior*, not stated ideology
+- A right-wing motion can have high centrist support while still being in a "right-wing" cluster if centrist parties split on it
+- Topics with cross-partisan agreement (defense, nuclear energy) show minimal spatial separation regardless of how radical the motion text is
+
+## When to Apply
+
+- Before interpreting any SVD/PCA spatial drift as "ideological shift"
+- When presenting SVD movement findings to non-technical audiences
+- When cross-referencing voting-pattern results with content-based analysis (LLM extremity scores, mechanism classification)
+
+## Prevention
+
+Always pair SVD drift findings with a caveat: "SVD positions reflect voting patterns, not policy content. We measure behavioral shifts in voting coalitions, not ideological repositioning of party platforms."

reports/overton_window/overton_window_synthesis.md

@@ -46,6 +46,8 @@ This is spatial *divergence*, not convergence. Centrist parties did not become r
 
 The tension between greater voting support and greater ideological distance is the puzzle that the mechanism analysis resolves.
 
+**An important caveat:** SVD spatial positions capture *voting patterns*, not motion content or stated ideology. The finding that centrists moved left on the SVD axes means centrist parties' voting patterns became more distinct from right-wing voting patterns — it does not tell us whether the motions themselves became more right-wing or left-wing in content. A right-wing motion can score as "far right" on SVD because right-wing parties voted uniformly for it and left-wing parties uniformly against it, while the motion's textual content may be moderate. Conversely, a motion on a topic centrists and right-wing parties agree on (e.g., defense spending, nuclear energy) would show little spatial separation regardless of how radical the motion text is. SVD measures agreement structure, not policy positions. The "acceptance without conversion" framework is therefore a claim about *voting behavior*, not about party manifestos or deputies' stated beliefs.
+
 ---
 
 ## Indicator 3: Content Extremity