The Education Week Research Center recently created a composite “Early Education Index”, and applied their measure to each of the fifty states and the District of Columbia.
A state’s overall index score is an unweighted average of eight indicators of early education. No states mandate preschool attendance, and most 3- and 4-year-olds are not enrolled.
For 2015 the highest composite score is 89.5 (of 100) for D.C.; the lowest is 56.7 for Utah. The five Pacific states are defined here as California, Arizona, Nevada, Oregon and Washington.
All five states are below the U.S. average score, and place in the bottom quartile of states. Details of the index construction are at: http://www.edweek.org/ew/articles/2015/01/08/states-graded-on-indicators-for-early-years.html?intc=EW-QC15-TOC
One can quibble with the choice and measurement of components, or the weightings, but the overall impression that Pacific states lag the rest of the country is likely to remain.