The American Community Survey (ACS) provides one-year (1y), three-year (3y)
and five-year (5y) multi-year estimates (MYEs) of various demographic and
economic variables for each "community", although the 1y and 3y may not be
available for communities with a small population. These survey estimates are
not truly measuring the same quantities, since they each cover different time
spans. Using some simplistic models, we demonstrate that comparing different
period-length MYEs results in spurious conclusions about trend movements.