Accuracy analysis of long-term planning projections for Utah and its counties

Analyzing the accuracy of half a century of planning projections in Utah demonstrates the challenges of long-term modeling in a state where population growth and change have been constants. At the state level, series have both under and over projected the population. The 1980s were characterized by over projection, on average. From 1990 to 2010, series tended to under project the population. Series produced since 2000 tend to over project the population. While these trends hold true, individual projection series error differs widely and is more variable at the county level.