Can we talk about how hard it is to find a prep cook who shows up on time?

I run a small bistro in Portland and I have gone through four prep cooks since March. Two quit without notice, one kept showing up 20 minutes late every shift, and the last one just stopped answering texts after a Friday night rush. I pay $18 an hour, which is above what most spots around here offer, and I still cannot keep the position filled for more than a few weeks. The last guy I hired had six years of line experience on his resume but could not dice an onion without turning it into mush. Is anyone else seeing this in their city, and what are you doing to find people who actually want to work the back of the house?