FANS of “American Idol” might be surprised to learn that, if sales figures are any indication, the real music capital of the world may not be America, but Luxembourg. Luxembourg is a tax haven, and Apple funnels more than a billion dollars worth of iTunes sales through that tiny country to avoid paying higher taxes.

These tax strategies are nothing new — and, no doubt, Apple has taken advantage of tax rules that allow them. The Senate’s Permanent Subcommittee on Investigations in 2008 estimated that at least $5 trillion to $7 trillion was sheltered in offshore jurisdictions like the British Virgin Islands, the Cayman Islands, Gibraltar, Bermuda and the Bahamas — not just by Americans, but by everyone. These jurisdictions have little or no income tax.

The favorable tax rates encourage corporations to avoid paying American taxes by structuring complicated international transactions, like Apple’s “Double Irish With a Dutch Sandwich,” recently described by The New York Times. But it’s not just the low tax rates that make these jurisdictions attractive to those following the rules. The secrecy of offshore jurisdictions allows some individuals and corporations to engage in outright tax fraud, costing America at least $40 billion each year.

And that secrecy makes offshore tax fraud almost impossible for law enforcement to detect. When I was the Manhattan district attorney, we learned of offshore accounts only through whistle-blowers, cooperators and serendipity.