two proportion z test with large population I want to test for differences between two proportions, specifically, a complete count of the number of events occurring within a population in year 1 vs that in year 2. I thought a two proportion z test would be appropriate. However, the size of the denominator is very large and consistently results in a small test statistic and significant results. Is there an adjustment or method to account for the large population size? Is there a different test that is more appropriate?
P = ((B1p1)+(B2p2))/(B1+B2)
Test Statistic (alpha=0.05) = 1.96 * sqrt [(P*(1-P))*((1/B1)+(1/B2))]
B1 = 2.02billion; p1 = 15.5%
B2 = 2.04billion; p2 = 18.2%
Percent difference = 18.2%-15.5% = 2.7%
P = 0.16857
Test statistic = 2.3E-05
2.7% > 2.3E-05 -> significant


Is there an adjustment or method to account for the large population size?

This is a feature, not a bug.  Immense sample sizes yield enormous precision, and so the change is likely "statistically significant" (because no two years are exactly alike, so the null is a straw man to start with) but may not always be practically significant.
