GUY RAZ: Lawmakers have spent a lot of time lately debating what to do about the country's growing deficit. In doing so, they're wrestling with the question that goes back to the beginning of the Republic: What should the government spend its money on?

Well, fear not. There is actually consensus among most economists on at least two things they say governments should pay for: lighthouses - and probably autopsies.

David Kestenbaum, of our Planet Money team, reports.

DAVID KESTENBAUM: Lighthouses are the classic example of what economists call a public good.

PROFESSOR CHARLIE WHEELAN (Public Policy, University of Chicago): Public good is something that we all need, that will make our lives better - but that the market will not and cannot provide.

KESTENBAUM: This is Charlie Wheelan. He teaches public policy at the University of Chicago. Think about lighthouses, he says. If the government doesn't build lighthouses, where would the money come from? Sure, someone could go around to ships' captains and say: Hey, we're going to build the lighthouse; want to contribute? But people will just say: No, thanks, I don't need one. I'm a good sailor.

Prof. WHEELAN: And you're just going to use our lighthouse without paying for it - because we can't do anything. We can't say, close your eyes when you sail past this rocky point.

(Soundbite of laughter)

Prof. WHEELAN: With every other good, if you don't pay for it, if you don't buy the sneakers at Walmart, you just don't get to walk with them out of the store. And if you do, we'll arrest you. We can't do that for the lighthouse.

KESTENBAUM: That seems like a sound argument, but we did some checking anyway.

OK, Jeff. Give us name and credentials.

Mr. JEFF GALES (Executive Director, U.S. Lighthouse Society): Jeff Gales, U.S. Lighthouse Society executive director.

KESTENBAUM: Jeff Gales says this is basically right. There were some privately built lighthouses. Then in 1789, the government set up what would become the U.S. Lighthouse Service.

Mr. GALES: Prior to the establishment of the U.S. Lighthouse Service, I mean, you didn't have lighthouses on rocky shoals or in the middle of the ocean. I mean, those are places where it was really expensive to build.

KESTENBAUM: So, general agreement on lighthouses. Also, most economists would agree it makes sense for governments to pay for a military, since that won't arise on its own; ditto with a court system.

Charlie Wheelan says some unexpected things also count as public goods, like autopsies.

Prof. WHEELAN: The Journal of the American Medical Association has been arguing for 15 years, at least, that there's a public health problem because we're not doing enough autopsies. The autopsy rate has plummeted from 40-some percent down to, I think, single digits.

KESTENBAUM: If we add more autopsies, we'd know more about how people die. So collectively, we all want them. And yet, no individual really has an incentive to pay for one. They don't see the benefit.

Prof. WHEELAN: There's none for the person being autopsied. It's a little late for that.

KESTENBAUM: The family thinks yuck, autopsy - which leaves the doctor. But think about it from the doctor's perspective.

Prof. WHEELAN: Best case, what you find in the autopsy confirms the diagnosis. Then, yes, I was right. It turns out it was this kind of cancer and so on. It turns out to be extremely common, much more than you would think, that there were either undiagnosed conditions, misdiagnosed conditions. So this person, best case he was right, worst case he's going to be looking at malpractice. So the person who is in the best position to encourage autopsy often will not.

KESTENBAUM: So you argue this is basically a lighthouse.

Prof. WHEELAN: This is a lighthouse.

KESTENBAUM: Charlie Wheelan did find one private company that does autopsies. So we called 1-800-Autopsy. We got Vidal Herrera, the founder.

Mr. VIDAL HERRERA (Founder, 1-800-Autopsy): The American people are our customers. Anytime a death occurs, if they don't have anybody to do an autopsy, they can call 1-800-Autopsy, and we'll help them.

KESTENBAUM: But even Herrera agrees the government should be paying for autopsies.

So there. We now have the beginning of an economist-approved list of things the government should be doing: autopsies, lighthouses, courts, defense.

But then, Wheelan says, we get to the hard questions. How much for defense? What about health care? Education? Those don't meet the strict definitions of public goods, but most governments end up getting involved with them anyway.

David Kestenbaum, NPR News.