Well, no economic engine does, these days, in the era of globalization. It’s all relative.
But the fact is that Catalonia *IS* the industrial area of Spain. (You didn’t think that the Spaniards were willing to go to war to keep an agricultural province, did you?)
Now, of course, Madrid is also a center of industrialization, but if Catalonia were to secede……..the standard of living for the other 80% of Spain would suffer, not the other way around.
(Catalonians, I’ve heard, tend to think of the Spaniards as just reaping the benefits of their hard work ethic. Don’t know how true it is, but I’ve heard that repeated on occasion on some of my business trips in the region.)