The city of Shenzhen launched a carbon trading scheme on 18 June, the country's first market for compulsory carbon trading. The scheme covers 635 industrial companies and some public buildings that account for about 40 percent of the city's carbon emissions. Under the trading program, those which emit below their quotas can sell their excess limits to other emitters and even investors, for profit. The carbon intensity, or the amount of carbon produced per unit of gross domestic product, of the 635 industrial companies, is estimated to come down by 32% by 2015, as a result of pressure being placed on emitters.