I doubt that it is very high. With typing now the norm rather than the exception, print handwriting will be forever dominant over script. Pilot, will soon overtake script as the number 2 form of penmanship in the United States. The biggest problem with teaching kids cursive writing is it takes the place of ensuring better penmanship. I can't tell you how many times I get notes from co-workers, colleagues, and friends that I can't read.
Important messages are indecipherable and beautiful post-cards contain cryptic messages.
If people would focus, just a little bit, on improving their handwriting rather than learning a new handwriting style, messages would be a little clearer. So my suggestion is to scrap cursive writing altogether. Stop wasting third graders time when you could be teach more math, spelling, reading, government, or typing. Getting rid of cursive writing won't make the world a significantly better place or solve world hunger or create lasting peace, but it will ensure that written documents will be more legible.