(FORTUNE Magazine) – Moody's, the credit-rating agency, recently downgraded Japan's public debt to A2, five rungs below the AAA rating that Japanese bureaucrats believe is their country's birthright. As a credit risk, this puts Japan, a nation whose public debt level is approaching 140% of GDP, below Botswana.

That the debt of the world's second-largest economy is rated riskier than that of a developing African nation drives Tokyo's economic gurus crazy. In fairness, they have a point. If you really think Japan is more apt to default on its domestic debt than Botswana, we've got a diamond mine we'd like to sell you. So, with apologies to David Letterman, here are the top five ways to tell Japan from Botswana. --Bill Powell

5. Botswana has natural resources like diamonds, copper, nickel, and coal. Japan has fish.

4. Revenues from Japan's annual auto exports alone exceed Botswana's GDP ($10.4 billion).

3. The percentage of people living below the poverty line in Botswana (per capita income: $6,600) is 47%. In Japan (per capita income: $25,000), it's less than 5%.

2. Botswana's biggest social problem: one of the highest rates of HIV infection in the world. Japan's biggest social problem: figuring out how to keep its best baseball players from defecting to the U.S.

1. Botswana's banks are solvent.