Don C. Brunell

Ever since the $15 wage proposal was narrowly approved by City of SeaTac voters, municipal leaders in neighboring Seattle have pushed to impose the same edict.

Washington already has the nation’s highest starting wage of $9.47 an hour and the state legislature is considering hiking it to $12, but Seattle Mayor Ed Murray and some city leaders want to peg it at $15.

Starting April 1, large businesses in Seattle — defined as those with more than 500 employees — will be required to raise the minimum wage they pay their employees to $15 an hour over three years. On the other hand, smaller businesse...