By David Cay Johnston

The views expressed are his own.

A new report from London and President Barack Obama’s statements to “60 Minutes” show financial crimes spreading like wildfire and governments failing to stop them.

Tax evasion equals 18 percent of global tax collections, a new report by British accountant Richard Murphy shows. His report for the Tax Justice Network cleverly lined up a World Bank Report on the size of shadow economies with a Heritage Foundation report on average tax burdens by country to reach that figure.

Murphy’s $3 trillion estimate, 5 percent of the global economy, shows how a combination of weak rules on accounting and disclosure combined with inadequate budgets to enforce tax laws impose a terrible cost on honest taxpayers and the beneficiaries of government service.

While the United States has one of the most effective tax regimes, especially for on-the-books wage earners and pensioners, and one of the smallest underground or shadow economies, it has the largest amount of tax evasion measured in dollars.

Murphy’s report covers 145 countries that generated $61.7 trillion of gross product, 98.2 percent of the world total. The 145 countries had only 61.7 percent of world population, a reminder of how poor the more than 2.7 billion people in the other 90 countries are.