These statistics on who’s leaving what states are somewhat misleading. Everyone knows people are leaving the Northeast and Midwest U.S., it’s been happening for 60 years. What would be more instructive is to look where CA ranks with the high growth sunbelt and western states (FL, TX, NM, AZ, NC, GA, TN, WA, OR, ID, CO, NV, UT, OK). I would bet it’s towards the bottom of that pack.
Also you have to look at who is leaving and who is coming in in terms of demographics (income level, educational level, etc…)