You don’t actually need a co-founder (2016)

That could be the case but my theory is that it's about control. Investors funded a solo founder before and then when they said to take some action (sell/pivot/scale up) the solo founder didn't do it.

They said damn this guy owns 70% of the company after Series A, we can't make him do anything we want! Now if there were 2 founders each founder would only own 35% of the company, and if they could convince one of those two founders they could get what they want. All investors want cofounders because they want more leverage. So if some investor is urging you to team up with a cofounder to 'complement your skillset' it might actually be that they aren't confident in your leadership and want an option to override you.

Is the Crunchbase data accurate? It's not like it's an official SEC report.

I always figured it would be missing lots and lots of data, seeing how it's self reported, and founders are likely to be something left out due to falling out and what not..

I think, at its core, the reason a co-founder is suggested is a person's internal dialogue is often different than the dialogue they have with others. Probably different parts of the brain (at least in part) get used when we speak with others than when we speak to ourselves.

Anecdotal evidence: How often have you gotten stuck on a problem, but as soon as you start explaining it to someone else you immediately know the answer?

Maybe those who are successful as entrepreneurs without co-founders have learned to exercise both of these dialogues alone?

Survivorship bias. What we don't see is the total proportion of failed startups.

If 95% of solo-founded startups fail outright before raising any venture capital, but only 80% of co-founded startups do, these numbers don't really mean anything -- you're better off finding a co-founder in terms of raw career success and entrepreneurial potential.

The only relevant information here is that once startups have gone through some sort of basic fundraising filter, solo-founded startups are more common than not. I would hazard a guess that there are a lot more solo-founded startups at the top of the funnel than in stage two. Let's see attrition rates at each stage (Founded, Angel, Seed, Series A, Series B, [...], Exit).

(That said: I generally agree with the statement that you don't need a co-founder. If you have the ability to execute, build and let a co-founder "find you" if necessary.)

To build a successful startup, you don't have to get a co-founder. What you need is a team.

If you are able to get things off the ground, doing 0 to 1 all by yourself, then you don't need a co-founder. But doing 1 to N, you need a team.

I had a co-founder in my first company, and we were very unproductive, as reaching consensus took a lot of time.

Then I started my second company without a cofounder. Things get way better this time. I'm an engineer and I get to build things quickly. The only downside of founding company alone is, raising money may take longer. Investors typically discriminate sole founder. But it's not impossible. There are still investors willing to take a bet on sole founders if you are able to prove that you are capable enough.

It's more possible than ever to start a company alone, especially when you know how to write code. Think about this, which is faster: a business person learns coding, or a programmer learns business skills?

Edit: adding this --

It becomes easier to start a tech company as a sole-founder nowadays, e.g., cheaper to bootstrap, commodity of tech stack / cloud infra, tons of advices on the internet, Stripe Atlas... I suspect that when this generation of sole-founders succeed, some of them will become VCs and they'll have more empathy on sole-founders and will bet on more sole-founders like them.