Malden has a large Asian population, estimated at more than 23 percent of the nearly 60,000 residents. In a stretch of Pleasant Street in Malden Square — from the MBTA station to Main Street — there are 19 Asian-owned businesses, four of which opened in the past 14 months. Another four are scheduled to open this year. They are filling up storefronts in Malden Square, bringing the vacancy rate to nearly zero, and playing a major role in the city’s downtown revitalization efforts. Those plans include tearing down City Hall to reopen Pleasant Street and replacing it with apartment buildings that include street-level commercial space.