"Putting a dent" in something means you've consumed or taken a very small percentage of a larger thing. For instance, "I've eaten three pieces of pie, but I have barely put a dent in it" means it is hard to see that you've taken or consumed any of it. Putting a dent in the economy means that money was taken out of the economy. It had a negative financial impact of $20 million dollars in the economy. However I'm not sure what this is trying to say. Are you saying that $20 million of the economy is a small amount or a large one? Saying "put a dent of only $20 million" would be a more natural way of saying a small amount, where "putting a hole of $20 million" would be the way to say it made a large impact. Edit: John is right. A dent is usually used as a positive term (or neutral like my pie example), a hole is usually negative.

In this context, it means "caused the economy to lose $20 million." In other contexts, "put a dent in" is a good thing. It means to make progress against some goal. Example: "In the last year, my wife and I have really put a dent in our credit card debt. We used to owe $5,000, but now we only owe $2,000."