Approximately ~73% of crowdfunders I have backed across nearly 8 years, have been successful and delivered a product. Of the others, ~3% were cancelled, ~9% didn't hit the target, and ~6% were successful but didn't deliver. Not bad going. I keep a public track of them in a makeshift spreadsheet - https://docs.google.com/spreadsheets/d/1_--0TYP3TD7i6dPnJmB9oB66iuU9_qS7ApBtKTS8bug/edit?usp=sharing