Question: The group that were the singing voices of the Be Sharps on The Simpson's episode "Homer's Barbershop Quartet" have performed at Walt Disney World since what year?
Sentence (from "The Dapper Dans"): The Dapper Dans are a barbershop quartet that performs at Disneyland in Anaheim, California (since 1959), at the Magic Kingdom at the Walt Disney World Resort (since 1971), and at Hong Kong Disneyland in Lantau Island, Hong Kong (from 2005 to 2008).
Relevant evidence: Yes