Antitrust Radar
Trend observatory

Economic observatory / concentration mechanics

Which share movements changed HHI?

Explain HHI change through the arithmetic contribution of each published participant category. Residual assumptions and source releases remain visible; arithmetic is not a causal explanation.

Default bridge previewSearch engines / 2023-2026-591 HHI
20237,950highly concentratedShare-squared change-591-591 to -591 possible20267,359highly concentrated
2023-591HHI2026
  1. Google Search-3.72 share points-647.43
  2. Bing+3.39 share points+55.09
  3. Yahoo Search+0.34 share points+1.70
  4. DuckDuckGo-0.24 share points-0.89
Markets
4
Source releases
16
Year pairs
24
Adjacent ledgers
12
Search engines2023-2026Browsers2023-2026Mobile operating systems2023-2026Social referrals2023-2026
Open derived dataset

Share-squared identityEach selected scenario reconciles participant contribution changes to the ending HHI minus the starting HHI.

Descriptive, not causalThe bridge explains index arithmetic. It does not identify conduct, liability, competitive effects, or consumer harm.

Participant contribution desk

Explain the HHI change

Attribute a definition-stable concentration movement to published category-share changes, then keep residual uncertainty and source custody attached.
Comparison window
Threshold reference
Selected HHI change+1,6022023 to 2026 · 4 residual firms
Starting HHI3,393Highly Concentrated
Ending HHI4,995Highly Concentrated
Possible change interval+1,602 to +1,602Increase is residual-robust
Largest contributionFacebook+2,053.92 HHI points

2023 Merger Guidelines · thresholds classify the endpoints but never change the share-squared attribution.

Contribution bridge / HHI points

Social referrals · 2023 to 2026

Increase stable
20233,393
HHI change+1,602
20264,995
Participant contributions to the Social referrals HHI change from 2023 to 2026Bars to the right increased HHI and bars to the left reduced HHI. The selected scenario changes by 1602 points and reconciles with a gap of 0.-2,0540+2,054Facebook51.95% → 68.94% · Continuing category+2,053.92Facebook: share 51.95% to 68.94%; HHI contribution change +2,053.92 points.Twitter / X19.47% → 11.63% · Continuing category-243.82Twitter / X: share 19.47% to 11.63%; HHI contribution change -243.82 points.Instagram13.38% → 6.28% · Continuing category-139.59Instagram: share 13.38% to 6.28%; HHI contribution change -139.59 points.Pinterest11.46% → 7.53% · Continuing category-74.63Pinterest: share 11.46% to 7.53%; HHI contribution change -74.63 points.Reddit0.96% → 2.35% · Continuing category+4.60Reddit: share 0.96% to 2.35%; HHI contribution change +4.60 points.YouTube1.86% → 2.33% · Continuing category+1.97YouTube: share 1.86% to 2.33%; HHI contribution change +1.97 points.LinkedIn0.49% → 0.40% · Continuing category-0.08LinkedIn: share 0.49% to 0.40%; HHI contribution change -0.08 points.Fark0.07% → 0.16% · Continuing category+0.02Fark: share 0.07% to 0.16%; HHI contribution change +0.02 points.Tumblr0.27% → 0.29% · Continuing category+0.01Tumblr: share 0.27% to 0.29%; HHI contribution change +0.01 points.Hacker News0.04% → 0.09% · Continuing category+0.01Hacker News: share 0.04% to 0.09%; HHI contribution change +0.01 points.Other social referrals0.05% → 0.00% · Aggregate residual0.00Other social referrals: share 0.05% to 0.00%; HHI contribution change 0.00 points.VKontakte0.01% → 0.00% · Exited observed share0.00VKontakte: share 0.01% to 0.00%; HHI contribution change 0.00 points.
Raised HHI contributionReduced HHI contributionAggregate residual assumption

Across the possible +1,602 to +1,602 HHI interval, the direction remains increased. 6 published categories raised HHI contribution and 4 reduced it.

Evidence handoff

U.S. social-media referral traffic

United States · 2023 and 2026 exact source releasesStatCounter Global Stats · StatCounter Global Stats

HHI contribution changes are descriptive share-squared arithmetic, not causal estimates. A participant's contribution can rise or fall because its observed share changed; the decomposition does not establish conduct, competitive effects, liability, or consumer harm. Aggregate residual categories remain sensitivity assumptions rather than observed firm distributions.