The Washington, D.C. minimum wage hike is already negatively impacting jobs in the city.

1,400 restaurant jobs have been lost in the last six months, according to a new report from the American Enterprise Institute. This is the largest and fastest loss of restaurant jobs in the city in since the 2001 recession.

The D.C. minimum wage increased to $10.50 an hour on July 1, 2015, and in July of this year it went up another dollar to $11.50 per hour. The minimum wage is set to increase by $0.70 per year until it hits $15 in 2020.

In the nearby Virginia and Maryland suburbs that have lower minimum wages, restaurant employment grew by nearly 3,000 jobs in the last six months.

The state minimum wage in Virgina is $7.25 per hour. In Maryland, the state minimum wage is $8.75 an hour and $10.75 in Montgomery County and Price George’s County.

“While it might take several more years to assess the full impact, the preliminary evidence so far suggests that DC’s minimum wage law is having a negative effect on staffing levels at the city’s restaurants,” the report said.

AEI scholar Mark Perry pointed out that D.C. has one of the highest costs of living in the nation, and if the city is already struggling to adapt to an $11.50 minimum wage, lower-cost cities like Minneapolis and Cleveland will face far more problems getting to $15.

California and New York have already passed laws raising the minimum wage to $15 an hour, and many other states are considering similar legislation. Senator Bernie Sanders has introduced a bill that would increase the federal minimum wage to $15, and the Democratic Party added a $15 minimum wage to its 2016 platform.

The Heritage Foundation recently put together a report on the state-by-state impact of a $15 minimum wage.

"The policy would result in many states losing hundreds of thousands of jobs and would considerably curtail employment opportunities, especially for less-skilled workers," said James Sherk, a research fellow at Heritage's Labor and Economics Center. "These findings show that the federal government should not impose a $15 minimum wage on states, and states should expect that adopting this policy would hurt many workers."