WASHINGTON

A trick question: If Congress takes no action in coming years, what will happen to the budget deficit?

It will shrink — and shrink a lot. This simple fact may offer the best hope for deficit reduction.

As federal law currently stands, some significant tax increases are set to take effect in coming years. The most important is the scheduled expiration of the Bush tax cuts at the end of 2012.

Of course, both parties favor the permanent extension of most of those tax cuts — the ones applying to income below $250,000. Both parties also oppose big cuts to the military, Social Security and Medicare, at least in the short term. Unfortunately, the deficit is likely to remain frighteningly large over the next decade without either cuts to those programs or tax increases.

Democratic and Republican leaders alike dance around this point. President Obama may call for “tax reform” in his deficit speech on Wednesday. He may even suggest that tax reform can reduce the deficit. He is very unlikely to explain which taxes will go up in his vision of reform, aside from some of those on the affluent. And while those increases will certainly help, they’re not enough.