Denmark has a constitutional monarchy and joined the EU in 1973. Its main industries include food, chemicals, machinery, and transportation. Tourism also plays an important role in Denmark's economy. Historically, Denmark was invaded by Vikings between the 8th-10th centuries, and today Denmark provides strong social protections for its citizens. Famous Danish people include the author Hans Christian Andersen and experimental film director Lars von Trier. Traditional Danish foods include smørrebrød sandwiches and roasted potatoes.