Demand share — definition and formula

Last reviewed 2026-06-11.

The number

Demand share for a stack in a given week is the fraction of all tech postings that week that explicitly mention the stack. If 8,000 tech postings ran the week of April 6, 2026and 320 mentioned Rust, Rust's demand share that week is 4.0%.

The formula

demand_share(stack, week) =
  COUNT(DISTINCT job WHERE job mentions stack AND job posted in week)
  / COUNT(DISTINCT tech job posted in week)

Numerator and denominator come from job_skill_resolved rows of type = 'tech' joined to job.posted_at. Non-tech postings (e.g., recruiter, designer-only) are excluded from the denominator so stacks aren't artificially diluted.

What a healthy WoW delta looks like

  • ±0.5pp in a week — typical sampling noise for mid-volume stacks; treat as flat.
  • +1.0pp+ sustained over 4 weeks — meaningful rise; usually reflects a real hiring shift, not noise.
  • −1.0pp+ sustained — meaningful decline. Often lags a layoff cycle by 2–3 weeks.

Common misreadings

  • Confusing share with absolute count. A stack can gain share while losing absolute postings — if the overall tech market shrinks faster than the stack does. Always read share alongside the 26-week posting count on the same page.
  • Reading week-over-week for low-volume stacks. Stacks with <100 postings/week have noisy WoW deltas. Prefer the 4-week rolling delta or the monthly snapshot.

See it on a live page