the University of Massachusetts Amherst, proposes $50 billion in tax credits for energy efficiency retrofits and renewable energy systems; $46 billion in direct government spending for public building retrofits, mass transit, freight rail, smart electrical grid systems, and renewable energy systems; and $4 billion for federal loan guarantees to help finance building retrofits and renewable energy projects. The Center believes that clean energy investments would yield about 300,000 more jobs than if the same funds were distributed among U.S. taxpayers. The clean energy investments would also have the added benefits of lower home energy bills and reduced prices for non-renewable energy sources, due to the reduced consumption of those energy sources. Worldwatch Institute/UNEP Global efforts to tackle climate change could result in millions of "green" jobs over the coming decades, according to a 2008 study prepared by the Worldwatch Institute with funding from the United Nations Environment Programme (UNEP). The study found that the global market for environmental products and services is projected to double from $1.37 trillion per year at present to $2.74 trillion by 2020, with half of that market in efficient energy use. In terms of energy supply, the renewable energy industry will be particularly important. Some 2.3 million people have found renewable energy jobs in recent years, and projected investments of $630 billion by 2030 would translate into at least 20 million additional jobs. U.S. Conference of Mayors Also in 2008, the U.S. Conference of Mayors released a report that finds the U.S. economy currently generates more than 750,000 green jobs, while over the next 30 years, an emphasis on clean energy could result in a five-fold increase, to more than 4.2 million jobs. Engineering, legal, research, and consulting jobs currently dominate the green jobs in the United States and could grow by 1.4 million by 2038, while renewable electricity production will create 1.23 million jobs, alternative transportation fuels will add 1.5 million jobs, and building retrofits will create another 81,000 jobs. The report notes that most of today's jobs are in metropolitan areas, led by New York City; Washington, D.C.; Houston, Texas; and Los Angeles, California. Green-Collar Work in China Background In China, green-collar work is defined as “employment in industries, professions, departments and enterprises that on an average social level have low input, high output, low consumption, low emissions, recyclability, and are sustainable". With this definition, the main goal of green-collar work is to