ARE you confused about whether large federal budget deficits matter?

No wonder, when disagreement about deficits is popping up everywhere. Even among Republicans, there is no unity on this basic issue. Defending his recent proposal to freeze government spending, Representative John A. Boehner, the House minority leader, said, “We simply cannot afford to mortgage our children and grandchildren’s future to pay for this big government spending spree.” But Martin Feldstein, the Harvard economist, disagrees. An adviser to the past three Republican presidents, Professor Feldstein warns that failure to run large deficits would prolong the current economic downturn.

Because important policy decisions hinge on whether deficits matter, this is an opportune moment to take stock of what we know. The good news is that there is little disagreement among economists who have studied the issue. The consensus is that short-run deficits help end recessions, and that whether long-run deficits matter depends entirely on how government spends the borrowed money. If failure to borrow meant forgoing productive investments, bigger long-run deficits would actually be better than smaller ones.

In 1929, President Herbert Hoover thought that the best response to a collapsing economy was to balance the federal budget. With incomes and tax receipts falling sharply, that meant cutting federal spending. But as almost all economists now recognize, President Hoover was profoundly mistaken.

When a downturn throws people out of work, they spend less, causing still others to be thrown out of work, and so on, in a downward spiral. Failure to use short-run deficits to stimulate spending amplifies that spiral, causing further declines in tax receipts and even bigger deficits. That this path makes no sense is a settled issue.