In the first week of​ July, a record 1,100 people went to the local swimming pool. In the second​ week, 100 fewer people went to the pool than in the first week. In the third​ week, 130 more people went to the pool than in the second week. In the fourth​ week, 350 fewer people went to the pool than in the third week. What is the percent decrease in the number of people who went to the pool over these four​ weeks?