Well, none from the point of view of the nation as a whole, since we would be pushing seniors out of Medicare and into private insurance, which has substantially higher costs. True, it would reduce federal spending — but not by much. The budget office estimates that outlays would fall by only $125 billion over the next decade, as the age increase phased in. And even when fully phased in, this partial dismantling of Medicare would reduce the deficit only about a third as much as could be achieved with higher taxes on the very rich.

So raising taxes on the very rich could make a serious contribution to deficit reduction. Don’t believe anyone who claims otherwise.

And then there’s the idea of taxing financial transactions, which have exploded in recent decades. The economic value of all this trading is dubious at best. In fact, there’s considerable evidence suggesting that too much trading is going on. Still, nobody is proposing a punitive tax. On the table, instead, are proposals like the one recently made by Senator Tom Harkin and Representative Peter DeFazio for a tiny fee on financial transactions.

And here’s the thing: Because there are so many transactions, such a fee could yield several hundred billion dollars in revenue over the next decade. Again, this compares favorably with the savings from many of the harsh spending cuts being proposed in the name of fiscal responsibility.

But wouldn’t such a tax hurt economic growth? As I said, the evidence suggests not — if anything, it suggests that to the extent that taxing financial transactions reduces the volume of wheeling and dealing, that would be a good thing.

And it’s instructive, too, to note that some economies already have financial transactions taxes — and that among those who do are Hong Kong and Singapore. If some conservative starts claiming that such taxes are an unwarranted government intrusion, you might want to ask him why such taxes are imposed by the two countries that score highest on the Heritage Foundation’s Index of Economic Freedom.

Now, the tax ideas I’ve just mentioned wouldn’t be enough, by themselves, to fix our deficit. But the same is true of proposals for spending cuts. The point I’m making here isn’t that taxes are all we need; it is that they could and should be a significant part of the solution.