This can affect your ranking.
Google is very secretive so this info is from what I've been told by other web masters that this happened to them, I have no idea if this behavior kicks in at above or below 21%.
What happens is that Google will display just one site for this content (may be with other sites collapsed), if Google thinks the other site has more "authority" the other site rank for that content and not you.
Usually, but not always, scraper sites have low Google rank and so will not displace the original in the search results - but if your competitor has good Google rank you may be in trouble.
Now, if this competitor is a legitimate company from a country that respect copyrights you can probably send them a nice e-mail asking for the content to be removed followed by a not-so-nice letter from a lawyer demanding it will be removed. (I am not a lawyer, don't take legal advice from strangers on the internet)
At the end of the day, your only defense is to be better at SEO than your competitor.