The pre-2012 upward trend in affective polarization driven by elite sorting and demographic change demonstrates that powerful non-algorithmic drivers were already producing rapid polarization growth at the start of the framing window, making it less likely that algorithmic curation independently contributed an additional 10% within 2012-2024.

[NARROW-VARIANT] Affective polarization in the US has risen sharply since the 1980s, well before social-media saturation, establishing a pre-existing upward trend driven by non-algorithmic forces. Affective polarization has been accompanied by mass affective polarization since the 1980s driven by elite ideological polarization, well before social-media saturation. Non-white share, partisan sorting, and elite polarization are positively associated with cross-country affective polarization trends, identifying structural drivers that precede and are independent of algorithmic curation. Therefore (narrowed), The pre-2012 upward trend in affective polarization driven by elite sorting and demographic change demonstrates that powerful non-algorithmic drivers were already producing rapid polarization growth at the start of the framing window, making it less likely that algorithmic curation independently contributed an additional 10% within 2012-2024.

• Affective polarization in the US has risen sharply since the 1980s, well before social-media saturation, establishing a pre-existing upward trend driven by non-algorithmic forces.
• Affective polarization has been accompanied by mass affective polarization since the 1980s driven by elite ideological polarization, well before social-media saturation.
• Non-white share, partisan sorting, and elite polarization are positively associated with cross-country affective polarization trends, identifying structural drivers that precede and are independent of algorithmic curation.

These are challenges this argument’s reasoning pattern must still withstand. Answering them on Isonomia strengthens the argument.

• Could a different cause produce the same effect E in this case?Open
• Is there a plausible causal mechanism by which C could bring about E?Open
• How strong is the causal generalization linking C to E? Are there documented cases where C does not produce E?Open
• Are there intervening or confounding factors that could interfere with the causal chain from C to E?Open
• Is the apparent link between C and E merely a post hoc correlation rather than a causal relation?Open

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