If, like me, you count yourself among those who think the big banks have gotten off lightly for the carnage they’ve inflicted on the world’s economy, take heart: Calls for a global tax intervention to curb, or at least mitigate, banks’ risky behaviors are gathering force. The Wall Street Journal today reported that the International Monetary Fund, at the request of the Group of 20 nations, is looking into a new tax that could be imposed on the financial giants to help governments clean up the current mess and head off any future meltdowns.

The details of how such a project might work — even assuming it’s possible to get all of the G-20 on the same page — are still fuzzy. John Lipsky, deputy managing director of the IMF, envisages the tax as a kind of global deposit insurance system, according to the Journal article. A densely theoretical report from the Bank for International Settlements last month suggested that it’s possible to quantify the risk that any particular bank poses to the banking system at large, and recommended that any “systemic capital charge” levied on a bank should increase as that risk increases.

A simpler model that’s been gaining traction in the past few weeks is the Tobin tax, a minuscule flat percentage tax levied on all foreign currency transactions that was first proposed by American economist James Tobin back in the early ’70s. Even a tiny tax on the world’s fx trade could yield vast sums for a fix-up fund.

The latest supporter of a Tobin-like levy is Nobel laureate economist Joseph Stiglitz (though he wants the tax to apply to all asset classes, not just foreign exchange). Stiglitz has a resounding quote in a Telegraph article today: ”The financial sector polluted the global economy with toxic assets, and now they ought to clean out.”

No argument here. Whatever form the tax takes, it will be a move in the right direction. ###