80% of businesses fail in 5 years. There are many reasons, but the usual ones revolve around things like not understanding accounting, not putting in the effort, etc.

It's also true that many very successful people failed at business time after time before figuring it out. Fortunately, American culture doesn't look askance at people that fail at business and try again.

What percent of businesses fail because the owners don't understand accounting? What percent fail because they don't put in the effort? Where did you find this data?

Google "why businesses fail" and there's a lot of information.