But in today's voluntary and unsubsidized markets, such well-intended rules can hurt some of the people they are meant to help.

Those good drivers, he said, were then paying much higher premiums than good drivers in the voluntary market.

It was designed to perform the same function - provide coverage for motorists who could not get it on the voluntary market.

"They shouldn't have to pay over 1,000 percent more just because they have the misfortune of not being insured by the voluntary market."

Environmental organisations are using the voluntary market to create new renewables and improving sustainability of the existing power production.

This marks the Conservancy's shift from the voluntary market to the mandatory market.

In the voluntary market, a variety of industry standards exist.

The other main category of buyers on the voluntary markets are those engaged in pre-compliance and/or trading.

The voluntary offset market, by comparison, is projected to grow to about $4bn by 2010.

Some businesses and nonprofits in the voluntary market encompass more than just one of the activities listed above.