{
  "slug": "market-share-leader",
  "name": "Segment leader",
  "aliases": [
    "Leader",
    "Top domain by share"
  ],
  "definition": "The tracked domain holding the highest CTR-modeled search market share in a segment for the period, reported with its share value.",
  "category": "Search market share",
  "type": "derived metric",
  "unit": "competitor domain, with its share as a % of tracked search demand",
  "direction": "neutral",
  "verification": "verified",
  "calculation": "Every roster row's share value is collected, columns that are not finite numbers dropped, the list sorted by share descending on the PRECISE value, and the first entry taken as the leader, domain plus share, the share rounded to one decimal place for display. Computed in the MCP over values the semantic layer returns; nothing about the leader is asked of the warehouse.",
  "aggregation": "Not aggregatable. It is a selection over one period's standings; a leader across periods must be recomputed per period, not averaged.",
  "grain": "One segment × period × medium.",
  "dimensions": [
    "intent",
    "brand",
    "keyword",
    "page",
    "country",
    "device"
  ],
  "requiredFilters": [
    "segment_id",
    "selected_period",
    "source_medium"
  ],
  "sources": [
    "rank-tracking"
  ],
  "reports": [
    "search-market-share-report"
  ],
  "skills": [
    "market-share-review",
    "competitor-deep-dive",
    "monthly-exec-review"
  ],
  "verbs": [
    "market_share_overview",
    "market_share_query"
  ],
  "rungs": [
    "R2"
  ],
  "levers": [
    "L2"
  ],
  "questions": [
    "Who leads this segment?",
    "Did the leader change this month?",
    "Is the leader a direct rival or an aggregator?"
  ],
  "interpretation": "The leader is whoever takes the most results-page real estate for this tracked demand, routinely an aggregator, marketplace or forum rather than the rival named on an org chart. A surprising leader is usually correct and worth saying out loud.",
  "caveats": [
    "Only tracked domains can lead: an untracked competitor with a larger real presence will never appear.",
    "You can be the leader yourself; the standings mark your own row and exclude it from the competitor list.",
    "Leadership does NOT flip on rounding, the sort runs on the precise share values and only the displayed figure is rounded to a tenth. Two domains can therefore publish the same share and still have a determinate order, which reads as an arbitrary tie unless the ordering is explained."
  ],
  "freshness": "~1 day behind, Daily observation, available the following day.",
  "failureModes": [
    "Reporting a leader change as a market event when it is a roster change (a competitor added or removed from the segment).",
    "Explaining a leader-versus-runner-up ordering by the published shares when those two shares are equal after rounding.",
    "Naming a leader for a segment whose share columns are entirely unpopulated, the verbs return a stated no-data note instead."
  ],
  "notSameAs": [
    {
      "slug": "market-share-standings-rank",
      "why": "The leader is an identity (which domain is first); the standings rank is your own ordinal position in the same sorted list."
    }
  ],
  "related": [
    "search-market-share",
    "gap-to-leader",
    "market-share-standings-rank"
  ],
  "workflows": [],
  "lastVerified": "2026-08-04"
}