H1 in one picture — every major venue, month by month. Where the volume actually went, Jan → Jun:

The majors

— Kalshi: a relentless climb: $3.7B → $9.4B, peaking in June. Six straight months of growth, no wobble.

— Polymarket: stuck in a $3.2B–$4.8B range, dipped to $3.2B in May, rebounded to $4.3B in June. Flat while Kalshi ran.

The challengers

— Opinion: front-loaded and fading: $3.3B in January → collapsed to ~$380M by June. The entire −80% share drop is right here.

— Predict.fun: volatile: a $647M April spike, back down to $265M in June.

— Limitless: the quiet grinder: $47M → $327M by May, the cleanest growth curve of the small caps.

Bottom line: Kalshi's lead isn't a one-month fluke — it's six months of compounding. The majors pulled away while the challengers churned.