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-5912023 to 2026 · 4 residual firms
Starting HHI7,950Highly Concentrated
Ending HHI7,359Highly Concentrated
Possible change interval-591 to -591Decrease is residual-robust
Largest contributionGoogle Search-647.43 HHI points

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

Contribution bridge / HHI points

Search engines · 2023 to 2026

Decrease stable
20237,950
HHI change-591
20267,359
Participant contributions to the Search engines HHI change from 2023 to 2026Bars to the right increased HHI and bars to the left reduced HHI. The selected scenario changes by -591 points and reconciles with a gap of 0.-6470+647Google Search88.88% → 85.16% · Continuing category-647.43Google Search: share 88.88% to 85.16%; HHI contribution change -647.43 points.Bing6.43% → 9.82% · Continuing category+55.09Bing: share 6.43% to 9.82%; HHI contribution change +55.09 points.Yahoo Search2.33% → 2.67% · Continuing category+1.70Yahoo Search: share 2.33% to 2.67%; HHI contribution change +1.70 points.DuckDuckGo1.98% → 1.74% · Continuing category-0.89DuckDuckGo: share 1.98% to 1.74%; HHI contribution change -0.89 points.Yandex0.15% → 0.38% · Continuing category+0.12Yandex: share 0.15% to 0.38%; HHI contribution change +0.12 points.Ecosia0.07% → 0.11% · Continuing category+0.01Ecosia: share 0.07% to 0.11%; HHI contribution change +0.01 points.Other search engines0.16% → 0.12% · Aggregate residual0.00Other search engines: share 0.16% to 0.12%; HHI contribution change 0.00 points.
Raised HHI contributionReduced HHI contributionAggregate residual assumption

Across the possible -591 to -591 HHI interval, the direction remains decreased. 4 published categories raised HHI contribution and 2 reduced it.

Evidence handoff

U.S. search engine usage

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.