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

**Stage 1 — Blind analysis (ignore current market prices).**

Assumption and definition: for this analysis I read the market question as asking whether the *average annual* number of U.S. measles cases across the four-year Trump Administration (calendar years 2025, 2026, 2027, 2028) will be >= 1,000. If you interpret the threshold differently, the quantitative probability will change; I state the assumption explicitly because the original prompt does not supply a numeric cutoff.

Key facts (treated without regard to market pricing):

- *Observed surge in 2026.* By late May 2026 the U.S. was reported to be near 2,000 cases year-to-date, and Utah alone reported 663 cases in one concentrated outbreak. Those counts are far above the low endemic levels seen in many prior years and indicate an active, large outbreak with potential for further growth in 2026. - *Concentration and heterogeneity.* A substantial share of cases are clustered in discrete outbreaks (e.g., Utah). Measles spreads explosively where pockets of under-vaccination exist; once those pools are exhausted an outbreak can slow, but new clusters can ignite in other undervaccinated communities. - *Policy and systemic environment.* Recent policy moves and reported executive actions that de-emphasize childhood vaccines broadly, plus major reductions in international health programs (USAID program closures), increase both domestic hesitancy and global importation risk. Measles importations from international outbreaks are a major driver of U.S. resurgence when pockets of susceptibility exist. - *Epidemiological balance.* Measles is extraordinarily transmissible (R0 typically 12–18). High local vaccination gaps produce rapid large outbreaks; after the susceptible pool declines, cases often fall sharply. Public health responses (case isolation, outbreak vaccination campaigns, school exclusions) can blunt spread but often lag a rapidly growing wave.

Reasoned projection (blind):

- 2026 trajectory implies a full-year total very likely to exceed 2,000 cases. Conservatively projecting the outbreak through summer/fall and allowing for additional importations and secondary clusters, a plausible 2026 total is 2,000–5,000 cases. - 2025 likely contributed some cases (post-2024 importations and pockets), but absent a documented 2025 massive wave I assume 2025 is lower than 2026 (hundreds to low thousands depending on when outbreaks began). 2027–2028 are uncertain: two plausible pathways are (a) continued elevated endemicity with multiple outbreaks seeded by lowered vaccination and global conditions, which would keep annual counts high (1,000+), or (b) one-off 2026 spike with reversion to lower levels as pockets are re-immunized and outbreak response occurs. - Balancing these, the *most defensible single estimate* is that the four-year average annual count will exceed 1,000 more often than not, driven primarily by a very high 2026 year. I therefore place an independent (blind) probability of ~72% that the 2025–2028 average annual measles cases >= 1,000.

Rationale for the point estimate (72%):

- *Upward pressure factors (higher probability):* - A confirmed ~2,000 YTD through May makes a multi-thousand total for 2026 plausible, which alone can lift the four-year average above 1,000 even if the other three years are moderate. - Policy shifts and international program wind-downs increase importation risk and domestic susceptibility trends over multiple years. - Pockets of chronic undervaccination (religious, philosophical, geographic) make recurrence likely — measles dynamics are not smoothed evenly across the population.

- *Downward pressure factors (lower probability):* - Outbreak burnout and aggressive local containment could substantially reduce total 2026 cases from the upper bound. - If 2026 ends up being a single anomalous spike and 2025/2027/2028 revert to low pre-surge levels (<500/year), the four-year average could fall below 1,000.

Netting those considerations, I judge 72% a calibrated, slightly conservative probability that multi-year average >= 1,000.

**Stage 2 — Market calibration (compare to current market prices).**

- Market snapshot: Yes = 0.30, No = 0.70. The market currently prices the event as unlikely (30% chance), significantly below my blind assessment (72%).

- Why the market might be lower (possible rationales): - *Ambiguity / wording risk.* Traders may be uncertain about the exact definition of "average" or the numeric threshold; ambiguity lowers willingness to take positions and depresses Yes prices. - *Recency skepticism / mean-reversion bias.* Many market participants may expect 2026 to be an outlier and therefore heavily discount a single-year spike's effect on a four-year average. - *Liquidity and participant composition.* The significant traded volume suggests interest, but particular large players or automated strategies might be skewing price toward No for risk-management reasons rather than belief about epidemiology. - *Conservative priors / loss aversion.* Traders may require stronger evidence that multiple years will remain high; they assign high weight to the possibility of containment and rapid reversion to baseline.

- Why I think the market may be mispricing the probability (i.e., market too low): - The market appears to underweight the magnitude of the existing 2026 wave and the systemic drivers (policy changes, global program cuts) that raise multi-year risk. A single year with several thousand cases materially shifts a four-year average upwards; markets might be focusing too much on post-spike mean reversion. - Ambiguity explanations are plausible, but even discounting a moderate ambiguity premium, the gap (72% vs 30%) is large and suggests a trade opportunity for someone willing to bear definitional risk.

Conclusion and actionable view: on my independent assessment the Yes outcome is more likely than market prices imply. If the market's definition matches my assumed threshold (>=1,000 annual average), I view Yes at 72% and the market at 30% as a substantial mispricing; if the market uses a substantially higher threshold, the disagreement could be explained. Verify the binary question's threshold and if it matches my assumption, the market likely underestimates the persistence and systemic drivers that will keep average annual cases elevated across the term.