This is the VOA Special English Economics Report.

Small business entrepreneurs play an important part in American job growth. Small businesses have created almost two-thirds of new jobs in the last 15 years. They also employ about 40 percent of the workers in high technology jobs.

The economy has traditionally been divided into three sectors. One is the private sector, meaning businesses. The second is the public sector, or government. And the third is the nonprofit sector.

But now some people talk about a fourth sector. It represents nonprofit and for-profit organizations working toward goals of social change and environmental activism.

Universities are starting to offer training and degree programs to prepare students to work in this area. One of these schools is Belmont University in Nashville, Tennessee. It now offers a degree in social entrepreneurship.

Bernard Turner is director of the Center for Social Entrepreneurship at the university. He says student interest is driving these new programs.

BERNARD TURNER: "Students are saying 'Now I want to be an entrepreneur, but I want to do something that deals with a social problem or a social issue that's dear to me.' So what happens is that a lot of these programs have come to fruition because they are student-driven."

William Paddock is founder and director of a business consulting company in Tennessee called WAP Sustainability. He has a business degree and training in the area of environmental sustainability.

Recently, the Custom Packaging company of Lebanon, Tennessee, hired him to help make its business more environmentally friendly. The company makes cardboard advertising displays for sales campaigns.

Mr. Paddock advised the company on recycling and ways to create less waste. He also persuaded the business to use electricity from solar energy.

William Paddock offers his consulting services for profit, but says social responsibility is a big part of what his company does.

WILLIAM PADDOCK: "For us it's really about protecting the environment, being better to society, but also there's an economic piece to it. We love to, you know, find our passions, but also save somebody money."

There are now more than 60 American universities offering so-called green business degrees.

The definition of social entrepreneurship and the exact nature of this sector continue to evolve. Some people are more interested in social programs and charity. Others are more interested in business plans and profits. But the root of the movement seems to be a desire to earn a living and make a difference at the same time.

And that's the VOA Special English Economics report, co-written by Mike Osborne. You can watch a video report on social entrepreneurship at voaspecialenglish.com. I'm Mario Ritter.

Related stories:

Ashoka supports social entrepreneurs around the world

US students bring honey project to Ghana

New group out to make a difference

A business plan for social change

（来源：VOA 编辑：崔旭燕）