The United States has a deficiency of public investment, says Nobel laureate economist Paul Krugman. And he puts the blame on Republicans in Congress.

"Nowadays we simply won't invest, even when the need is obvious and the timing couldn't be better," Krugman writes in The New York Times.

"Don't tell me that the problem is political dysfunction . . . Our inability to invest doesn't reflect something wrong with Washington. It reflects the destructive ideology that has taken over the Republican Party."

Consumers and businesses are saving instead of spending, and that's hurting the economy. "The mismatch between desired saving and the willingness to invest has kept the economy depressed. Remember, your spending is my income and my spending is your income, so if everyone tries to spend less at the same time, everyone's income falls," Krugman explains.

"There's an obvious policy response to this situation: public investment," he writes. "We have huge infrastructure needs, especially in water and transportation, and the federal government can borrow incredibly cheaply."

The problem is heated opposition to any sort of government spending. "It's all about ideology. This hostility began as an attack on social programs, especially those that aid the poor, but over time it has broadened into opposition to any kind of spending," Krugman argues.

"America has turned its back on its own history. We need public investment; at a time of very low interest rates, we could easily afford it. But build we won't."

Former Treasury Secretary Larry Summers sees a need for government spending on infrastructure too. He cites an International Monetary Fund (IMF) report to buttress his case.

"Most notably, the IMF asserts that properly designed infrastructure investment will reduce rather than increase government debt burdens," Summers writes in the Financial Times.

"Public infrastructure investments can pay for themselves. . . . Infrastructure investment actually makes it possible to reduce burdens on future generations."

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