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.

<iframe
  src="https://www.isonomia.app/embed/claim/426d8e3673439c8996d68e27fb0fd266053c32ebbea701599138d2c91b7a8ad9"
  width="600"
  height="280"
  frameborder="0"
  style="border: 1px solid #e5e7eb; border-radius: 8px;"
  title="Isonomia Claim"
  loading="lazy"
></iframe>

Copy and paste into any website or forum that supports HTML.