China's government now borrows far more cheaply than the US, a sign of trouble for American finances and a quiet win for Beijing.

• US borrowing costs for 10-year debt jumped more than a full point over the past year, while China's went down.
• China borrows at under 2%; the US pays over 5%.
• Expensive oil and inflation are the usual explanation, but China is the world's biggest oil buyer and its rates still fell — so oil is not the cause.
• The deeper split is what the money bought: China spent 20 years borrowing to build, including quadrupling its electricity output, while US power generation stayed flat.
• American borrowing went largely to wars and bank bailouts instead of things that produce lasting returns.

Outlook: Unless the US gets more out of what it borrows, its interest bill keeps climbing while China's stays cheap.