What will the average number of measles cases be during Trump's term?

**Stage 1 — Blind analysis (ignore market prices):**

The outcome hinges on arithmetic: the event asks for the 4‑year average across 2025–2028. That means early, large outbreaks in 2025 and 2026 have outsized leverage on the multi‑year average. CDC/NBC reporting that the U.S. already had ~2,000 cases by late May 2026 (roughly approaching or exceeding the 2025 total in just five months) implies a high likelihood that at least one of the first two years of the administration will be markedly above the recent historical baseline. Because measles is highly transmissible and can produce rapid, concentrated outbreaks in undervaccinated communities (and because a large share of cases are in adults, expanding the susceptible pool), the risk that cumulative counts in 2025–2026 will lift the 4‑year mean into whatever the market defines as the 'Yes' range is material.

Balancing that, public health responses are effective when mobilized: targeted vaccination campaigns, school/workplace requirements, outbreak isolation, and aggressive contact tracing typically suppress transmission once clusters are identified. If 2026 outbreaks decline in the second half of the year and 2027–2028 revert to lower historical rates (either due to targeted immunization or because susceptibles are transiently depleted), the 4‑year average could fall back under the threshold. Seasonal patterns, stochasticity of importations, and large but short-lived outbreak dynamics mean year‑to‑year variability is high.

Weighing the factors above, my independent (blind) assessment is that there is a better‑than‑even chance that the multi‑year average will be high enough to satisfy the 'Yes' outcome. I place that probability at **65%**. This reflects (a) the strong evidence of an unusually large early‑term burst through mid‑2026, (b) the expanded susceptible population implicated by adult cases, and (c) the arithmetic leverage of two high years out of four. I do not assume runaway exponential growth through every remaining month; instead, the projection rests on the observed elevated pace in 2025–mid‑2026 being sufficient to push the 4‑year mean above the market's threshold unless unusually strong suppression occurs in 2027–2028.

**Stage 2 — Market calibration (look at prices):**

The market's current price (Yes: 0.31 / No: 0.69) is materially lower than my independent 65% estimate. There are credible reasons the market might be pricing a lower probability:

- Market participants may anchor to long pre‑2024 baselines (many recent years had low case counts) and underweight the persistence risk from a two‑year elevated run. People often treat large early spikes as transitory and assume aggressive control will bring averages down. - Some traders may be correctly anticipating effective public health responses, rapid catch‑up vaccination campaigns, and nonlinearity in outbreak sustainability (i.e., rapid depletion of local susceptibles causing outbreaks to self‑limit), and they therefore price lower risk to the four‑year average. - Liquidity and trader composition can bias the market: a few large actors betting on 'No' or risk‑averse retail could depress the Yes price relative to fundamentals.

Given the strong early‑term data, I view the market as *undervaluing* the risk that the early surge meaningfully raises the 4‑year mean. In other words, if you accept the observed counts and the expanded adult susceptibility as persistent drivers, the current market price looks like an attractive buying opportunity for the 'Yes' side; fair value given my model is closer to the mid‑60s. That gap can persist if new information (rapid vaccination drives, sharp drop in 2H‑2026, or data revisions) comes in, but absent that, the market appears to be underpricing the arithmetic leverage of the high 2025–mid‑2026 totals.