In WA we used to have one of the highest exemption rates for kids going into K (6%). In 2011 a law passed that parents had to have a signed form from their doctor to do a philospical exemption. that made the rates drop significantly to 4.5% (So now under the 95% stat for "herd immunity" if herd immunity was applicable to pertussis which I still maintain it is not due to the inadequacy of the aP part of DTaP.)
However this year, AFTER our big rise in vaccination rates for kids, we are now in a pertussis epidemic. So I still don't see the correlation.
And the CDC has stated in the updated MMWR for "prevention of pertussis, diptheria, and tetanus in pregnant and postpartum women and their infants" that the vaccination compliance rates for DTaP are rising each year. That is where i got the 99% of all children are up to date on their vaccine status info from. So unless the CDC and WA DOH are lying, vaccination compliance rates are rising. But so are cases of pertussis.