[GianFabien]

What was the topic of your PhD?

I'm an EE with strong control systems and computing expertise, ended up doing business analysis, etc (more lucrative). After 20 years of that went back to do a PhD in SE. I'm now running a consulting business focusing on model based software engineering in both business and embedded systems domains.

Doing a PhD makes you the "specialist" in the chosen field. You need to apply that specialist knowledge to solve "important" problems to maximize the value you deliver. For example, many math PhDs have found jobs in banking because they are able to use advanced mathematical principles to model investments and markets. In so doing, they are able to pinpoint profitable trades.