Rates are so low … why aren’t we building our brains out?

Long-term rates are low and, even if the Federal Reserve raises rates this year, they're likely to remain at a low level for a long, long time. So, why aren't we building our brains out?

The real, or inflation-adjusted yield, on the 10-year Treasury note is hovering near zero — and just fell back into negative territory last week. That means the government can borrow money for almost nothing.

At the same time, our infrastructure is in desperate need of repair. Seems like a no-brainer to me.

It's not just about saving money and averting the next bridge collapse — infrastructure spending now will create jobs and boost the economy. In a recent New York Times column, Paul Krugman pointed out that the U.S. is in a classic liquidity trap – the Fed has lowered rates to near zero and yet it hasn't been effective in bringing the U.S. back to full employment. Investing in infrastructure would create a lot of jobs – notably for those who lack a four-year college degree, a group that was among the hardest hit by job loss during the recession and didn't fare much better as the economy started to recover.

The Obama administration did launch a fiscal stimulus program in 2009 to combat the effects of the Great Recession, a broad spending bill that included pumping money into states to plug budget holes (keeping policemen, teachers and other government employees on the job), extending benefits to the unemployed and investing in some infrastructure projects such as highway repair and bridge construction. However, the $800+ billion program was too small, and too targeted, to stimulate the economy and create jobs.

Former Treasury Secretary Larry Summers has mentioned aggressive fiscal stimulus as a means of fighting what he calls, "secular stagnation," a condition in which the economy grows below its potential for several years, if not decades.

Even Donald Trump, whose eclectic policy prescriptions have perplexed many, to put it kindly, has called for a rebuilding of an infrastructure currently more suited to the early 20th century than for the next 100 years.

Many have focused on not only rebuilding roads and bridges, but truly re-imagining what the guts of the U.S. economy should look like decades into the future.

Re-imagining and re-building our infrastructure means more than filling potholes and rust-proofing bridges. It means tearing up the blueprints for America's highways, bi-ways and information superhighways.

It means radically upgrading the nation's power grid; tearing down phone lines in our wireless world; burying power lines to reduce productivity-destroying outages; launching a new, smart interstate highway program, paving the way for autonomous cars; upgrading airports and railways, while making way for hyper-loops and supersonic travel.

That is a tall order — and an expensive one. But, in a world of historically low interest rates, it may be far cheaper than anyone currently imagines.

Experts have suggested that a complete overhaul of the nation's infrastructure would cost somewhere in the neighborhood of $3 trillion – and that's before we add in hyper-loops and other bells and whistles of the future. It sounds like a lot of money. But remember that China received nearly universal praise for spending close to $6 trillion in about five years to turbo-charge its own economy with a massive infrastructure buildout.

David Kotok, who heads Cumberland Advisors, and is an expert on the Fed, interest rates, and municipal finance, offers the following financing plan that is more than achievable: The U.S. Treasury can issue $4 trillion in 100-year inflation-protected securities (TIPS), with a nominal yield of 1 percent. That would mean investors would be funding it — as opposed to the government forcing the hand of taxpayers to cough up the money.

Investors, by the way, have been clamoring for high quality bonds with decent yields all across the planet. In fact, many argue that there is a shortage of Treasury bonds available for purchase. Banks, insurance companies and pensions, among others, would, no doubt, love to get their hands on some decent-yielding 100-year bonds to meet their capital — and actuarial — requirement!

Of course, 100 years is a long time — and it's rare for governments or corporations to issues bonds with such a high maturity. But, given the low cost of issuance, and inflation protection investors would get from a TIP, (a bond with a yield that rises as inflation goes up) could make the whole scheme not only feasible but attractive. The 100-year maturity would survive us all, but those bonds could be passed down as part of an estate, or fit comfortably in the portfolios of large institutions that truly invest for the long haul.

The interest expense on such a plan would be roughly $40 billion a year to start. According to most experts, that plan would rebuild the nation's entire infrastructure over 10 years. User fees, like tolls and excise taxes, would be applied to help to pay off those yields over the estimated lifespan of the projects.

Just look at the George Washington Bridge to see how user fees turn deficit-financed projects into profitable capital assets. The cash toll is $15 for cars (more for commercial trucks), going from New Jersey to New York. That, alone, brings in $700 million in annual revenue, according to the Port Authority of New York and New Jersey in its 2015 budget estimate.

Many economists and policy makers have suggested that a deal on corporate tax reform could help finance a so-called "infrastructure bank." That's a public/private pool of cash that can be used toward the overall expense of re-building America.Effectively, the pot could be sweetened with a 10-year corporate tax-repatriation holiday that would help fund that bank. If U.S. companies are given a tax break on money they bring back to the U.S. from overseas, then they can use that money to pay off debt, which could provide the seed money for such an infrastructure bank.

The final kicker is that such a program would give relief to all state and local budgets, many of which remain cash strapped and unable to afford to tackle the problem on their own.

I guess the only question left is: What are we waiting for?

Commentary by Ron Insana, a CNBC and MSNBC contributor and the author of four books on Wall Street. Follow him on Twitter @rinsana.

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