Question: Ole and Lena are central characters in jokes by which specific portion of  Americans, in the broad sense?
Sentence (from "Ole and Lena"): Ole and Lena (also Sven and Ole) are central characters in jokes by Scandinavian Americans, particularly in the Upper Midwest region of the U.S., particularly in Minnesota, Wisconsin, Iowa, South Dakota and North Dakota where Scandinavian immigrant traditions are common.
Relevant evidence: Yes