While American higher education remains the envy of the world, it is becoming unaffordable for many Americans.

How much greener is the grass in the US? This is not a question about medical marijuana and Santa Cruz. There, the city council has decided that whenever federal agents go to arrest the pot growers - who are licensed by the state but illegal in the eyes of the federal drug-enforcement agencies - a small stash of marijuana shall be left behind for medically approved users. I don't imagine Madison and friends anticipated that side-effect of federalism.

Since the upside of federalism from the point of view of higher education is very obvious - less interference from ignorant civil servants and their masters, more room for local experiment, an enormous range of institutions from wonderful to terrible, secular to sectarian, research-minded to remedial - a few gloomy thoughts about US higher education might be in order once in a while.

President George W. Bush is said to be weighing the electoral benefits of being nasty to colleges and universities. The obvious grounds on which to do it are high costs and high dropout rates. Tuition fees have risen at two to four times the rate of inflation for the past two decades. Even in public colleges and universities, tuition looks expensive when set against its historic cheapness. When I taught at Hunter College in New York in 1967, it was the tail end of the era of free tuition, but rigorous admissions requirements (so-called open admissions) came in soon after, and so did tuition fees. From this autumn, it will cost $4,000 (?2,460) a year for in-state students and $360 a credit for out-of-staters - that's about ?26,500 for the 120 credits it takes to get a degree.

É«ºÐÖ±²¥

The numbers are more vertiginous at private universities; between 1982 and 2002, tuition at New York University went up from $5,820 a year to $26,646 - a rise of 358 per cent against general inflation of 86 per cent. It's not only Bush who thinks it's all a bit much - these numbers were collected by Hillary Clinton's senior colleague, the impeccably Democratic senator for New York, Charles Shumer. Nobody quite knows why it has happened.

University presidents get paid a great deal - half a million or more at serious institutions - and so do star professors. But academic salaries have overall risen by little more than inflation and, as in the UK, have fallen (if less dramatically) behind the salaries of similarly educated white-collar workers outside academia. An army of deans and counsellors are blamed by some observers - but they, too, are paid rather little; incessant upgrading of computer facilities is blamed by others. But one way and another, higher education shares with healthcare an unenviable record in racking up cost increases - and, as with healthcare, it never seems that what you get is much better than before.

É«ºÐÖ±²¥

Dropout rates are an easy target, too. Only about half of all students get a four-year degree within five years; and the graduation rate among students from poor families is about 20 per cent. Ivy League schools and their peers graduate 95 per cent of their students in less than five years, which gives some idea of how bad things are for hard-up students at community colleges.

All the same, Bush's advisers know that it's risky attacking higher education. Americans think their higher education is terrific; they just think it's becoming unaffordably expensive. The trouble for the Republicans is that they have no idea how to make it less expensive, and no idea about how to improve the graduation rate without spending money. Since the present administration is adamant that government expenditure is a bad thing, and has given away the money that might have supported poor students in tax cuts for the rich, grandstanding is the only policy option they have left.

Congressman Howard McKeon of California is leading the way. He has just told The Chronicle of Higher Education that he is going to propose to make all colleges and universities report their price increases to the Department of Education; if they are above the retail price index, they will be told to hold them down. If they don't, they will face sanctions.

The only sanction the federal government has against private institutions is to make their students ineligible for federal financial aid.

É«ºÐÖ±²¥

Improving affordability by cutting student aid is an idea that only a California Republican could advance with a straight face. But, then, California has a budget deficit of $38 billion, a Republican minority in the legislature is preventing the passage of any budget whatsoever, and students are looking at tuition fee increases of 25 to 30 per cent from next month. No wonder there's such a demand for medical marijuana.

Alan Ryan is a fellow at the Center for Advanced Study in the Behavioral Sciences, Stanford University.