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Atmospheric CO₂ (Mauna Loa) vs US Health Expenditure

Atmospheric CO₂ (Mauna Loa) and US Health Expenditure correlate at r = +0.89 over 24 years (2000–2023), p < 0.0001. With the time trend removed, r = -0.48. Direction flips without the trend.

Verdict: Direction flips without the trend. The raw correlation is 0.89, but once each series' time trend is removed it becomes -0.48. The year-to-year movements run the opposite way to the long-run trends, so the headline number is misleading.

Pearson r
+0.89
p-value
< 0.0001
Years compared (n)
24 (2000–2023)
95% confidence interval
0.76 to 0.95
Correlation with the time trend removed
-0.48

Sources

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Correlation does not imply causation. How the verdict is worked out.