Despite the worldwide economic troubles of the last few years, more corporations than ever are embracing sustainability – and for good reason. A report published in November by global consultancy McKinsey concluded that better resource productivity could yield global savings of up to $2.9 trillion.

You can find out just which companies are leading the pack in Corporate Knights 2012 Global 100 ranking of the world’s most sustainable corporations.

If you look closely, you’ll see that some countries are home to more clean capitalism leaders than others. In this year’s ranking, the countries with the most leaders include the United Kingdom, with 16; Japan, with 12; the U.S. and France, each with eight; and Australia and Canada, tied at six. And Scandinavian firms made up five of the top 10, including the No. 1 most sustainable corporation, Danish healthcare company Novo Nordisk.

Why do some countries do better? One of the most obvious answers is regulation. All of the Top 5 countries require large emitters (at least) to report their carbon emissions. In addition, the European Union has run a mandatory cap-and-trade program since 2005, and has committed to reducing carbon emissions 20 per cent below 1990 levels by 2020. Japan pledged to cut carbon 25 per cent below 1990 levels by 2020, although it’s reconsidering that commitment after the Fukushima nuclear disaster. In August, the Japanese parliament also passed renewable-energy incentives aimed at boosting its solar, wind and geothermal power. And Australia in November passed legislation that fixes a price for carbon emissions and sets up an emissions cap-and-trade program starting in 2015.

But regulation is hardly the whole story. After all, many countries with strict regulations got few companies on the Corporate Knights list. The U.S. has little in the way of mandatory regulation. And, amid economic concerns, governments in the U.S., Europe and Japan have lowered their sights on stronger climate-change regulation in the last few years, said Aron Cramer, chief executive officer of BSR, a corporate responsibility consulting firm based in San Francisco, California.

Instead of cutting back their sustainability efforts in response, Cramer has seen many businesses in these countries step up. “As governments have gotten more timid, companies have gotten more aggressive,” he said.