Secondly, while I agree with you that if you planned everything by yourself and are willing to do it alone, you shouldn't just look for co-founder when you can start implementing by yourself with some employees. But I got to warn you that's pretty extreme and may get you looking like a 70 year old when you are 25 very fast, because of the exhaustion it causes to run a big venture by yourself.
I don't know statistics either and I would like to put  everywhere I look on the internet but a two men team has more potential on the long run then an one man army because the two founders motivate each other, share problems and have a larger knowledge base to solve them, make it more fun and pleasing to work on a startup.
I like your post because you raze awareness regarding the importance of having good cofounders. Anyway some people like to work alone one and they do it better that way, but I think most men might fall apart on such high pressure, especially if they don't have previous experience in making startups.
One more thing is that it's very hard to find good employees that are willing to work at a startup, even harder to pay them while you don't have any revenues in site.
No need to warn me, I've seen the strife of having co-founders, and I've seen the harmony of having a solo found er and co-founder teams that lasted 20 years.
I don't think its a factor of finding "good" co-founders. I think unless you have known the person a long time, you can't know if they are "good" or not- its not whether they are good or not, as the most earnest, responsible, loyal and considerate founder may still be the death of your company. Its fundamental to the nature of trying to manage a company by consensus.
Consensus management doesn't work- or we'd be up to our ears in all the communes the hippies started in the 60s and 70s.