Welch actually said 20 years. And when confronted about that performance he refuses to discuss it. That should tell you something.

DUBNER: Let me ask you this: in 1999, not long before you retired from G.E., you said that your ultimate success would be determined by how well your successor grows the company over the next 20 years. When you said that, G.E.’s market cap was up north of $450 billion. Now it’s almost 20 years later, it’s just north of $200 billion. So talk to me about that. I know that you —

WELCH: I don’t talk about that.

Now maybe Welch doesn't want to seem like he's bad-mouthing the performance of those who came after him, but he does have at least some responsibility for ensuring a good continuity of leadership.

https://freakonomics.com/podcast/extra-jack-welch-full-inter...