On the face of it, Greeks are some of the most industrious people in the world. Almost a third of the work force is self-employed. That's double the average of other Europeans who strike out on their own, and far above America's 7%.

But for all of their ambitions and effort, these same Greeks appear to be very bad at money management.

According to their personal income tax filings, on average self-employed Greeks spend 82% of their income on debt service, paying for things like cars and homes.

For comparison, the rule of thumb in the U.S. is that debt service should take up no more than 30% of income. After all, people have to eat, buy gas, pay for clothes, etc.

In Greece, the problem gets worse when we look at individual sectors. Ironically, business owners in accounting and finance manage to spend 115% of their income on debt service, making them the worst money managers in the bunch. Other professionals who spend over 100% of their income on debt work in medicine, lodging, retail, and transportation.

Before you shed a tear for these hard-working souls that can't seem to get ahead, you should know something: no one believes they're telling the truth, particularly their banks and the government.

The taxpayers lie to avoid taxes, and the effort to catch them sheds light on why bitcoin won't survive in its current form.

Like bankers everywhere, Greek bankers have to lend to make money. If they avoided all the self-starters who claim exceptionally low incomes to avoid taxes, then they would miss lucrative sections of the market.

So they did what any reasonable banker would do: they created their own model for estimating a person's real income based on what they reported to the government.

This approach proved so accurate that a group of academic researchers were able to use the data to determine how much tax revenue these professionals were withholding from the state. In 2009, the number was 11 billion euro, or roughly 12% of Greek tax revenue for the year.