The risk-weighting system is far too complex and too easily manipulated to provide a reliable picture of how much capital a bank really has. For a large bank such as JPMorgan, coming up with a risk-weighted ratio requires sorting assets into more than 200,000 different buckets. Even unintentional errors can skew reported capital ratios by several percentage points [sic, emphasis mine]. That’s a problem when the starting point is only 10 percent.

Banks in Europe are undercutting regulators’ demands that they boost capital by declaring assets they hold less risky today than they were yesterday.

Banco Santander SA (SAN), Spain’s largest lender, and Banco Bilbao Vizcaya Argentaria SA (BBVA), the second-biggest, say they can go halfway to adding 13.6 billion euros ($18.8 billion) of capital by changing how they calculate risk-weightings, the probability of default lenders assign to loans, mortgages and derivatives. The practice, known as “risk-weighted asset optimization,” allows banks to boost capital ratios without cutting lending, selling assets or tapping shareholders.