For the tens of thousands of high school seniors and their families now setting out on that ritual of American education, the college search, it's now official: The California Institute of Technology is the best university in the country.

And Swarthmore is the best liberal arts college.

At least that's what U.S. News & World Report magazine says in its annual college rankings, and while academics and many families pooh-pooh these numerical ratings--which purport to show that Caltech really is better than Harvard, which really is better than Yale, which really is better than Stanford, which really is better than Duke--it turns out that enough people take them seriously to have a major impact on the college application process.

A recent analysis of the ebb and flow of college applications over the past 15 years vs. the ups and downs of various colleges in the U.S. News rankings concludes that when a school moves up in the rankings, it attracts more and better applicants and obtains a higher "yield" (accepted applicants who come) from that crop. And when it moves down, the reverse happens.

In fact, the study found that it is possible to look at a school's change in position in the rankings year-to-year and predict just how much more (or less) selective it will be able to be the following year, how much its yield will improve (or decline) and how much the average SAT scores of income freshmen will rise (or fall).

Since colleges actually change very little in a year or two, these movements often are more the result of changes in the magazine's methodology than of a genuine rise or fall in academic quality.

Further, the study--by James Monks of the Consortium on Financing Higher Education and Ronald G. Ehrenberg of the Cornell Higher Education Research Institute and published by the National Bureau of Economic Research in Cambridge, Mass.--found that it is possible for an institution to tweak itself in ways that have "no effect on the institution's underlying academic quality" and move up in the ratings.

Cornell did just that, and it moved to sixth last year from 14th in 1997, the NBER study said. Though Ehrenberg declined to discuss exactly what the school did--he said editors of his forthcoming book have him under "a gag order" on the subject--the NBER paper noted that improvements in quantity and quality for this fall's freshman class were in line with predictions.

U.S. News noted in its rankings, which appear in the Aug. 30 issue, that it has again slightly altered its formula, partly in response to advice from school administrators and other experts.

Possibly as a result of that, Cornell slipped to 11th this year.

"The interesting thing is, this year Cornell did very well [in applications and admissions]. If you now go forward and say they dropped from sixth to 11th, we'll predict next year's class won't be quite as bright. That's really scary, because nothing has really changed over a two-to-three-year period in terms of what the university is offering," Ehrenberg said.

Ehrenberg said that while "many people don't pay much attention to" the rankings, "some people do, and it's those people that make the difference."

Part of the reason, of course, is the increasing shift in this country toward what has been called a "winner-take-all society," which is pressing families to seek out every possible advantage, no matter how small, for their children. Whereas colleges were once viewed in broad categories and it was enough for most people to go to a "good" school, today many families are fearful that anything less than "the best" will blight the student's life prospects.

And related to that, colleges, like medical care facilities, are notoriously hard to evaluate, so that a consumer is largely left with reputation, word of mouth and other subjective criteria in choosing a school.

It is into this vacuum that U.S. News has stepped.

But while research shows that there are advantages to going to a highly selective college, Ehrenberg said, "there's no such thing as a best institution for every student."

"The great difficulty is that these institutions are multi-product firms, and what is the best institution for any particular individual is going to vary widely across individuals. That's the real dilemma of this," Ehrenberg said.

Caltech, he noted, did well in part because it is well endowed and gets lots of additional money through scientific research grants, and its students are top-notch.

"But that doesn't mean that if there's a particular area of biology you are interested in that they will necessarily have it, or if you're a performance-music major they will have that. Or if you want to go to school in a rural area . . .," Ehrenberg said.

There are also other ways of ranking schools. The September issue of Kiplinger's Personal Finance Magazine, features its "Top 100 Values in Private Colleges," a ranking that takes cost into account.

Interestingly, Caltech comes out second on that list (behind Rice University) and Swarthmore is tied for sixth, but none of the Ivy League colleges makes it into the top 10. On the other hand, Washington & Lee, rated 14th on U.S. News's list of national liberal arts colleges, comes in fourth on Kiplinger's value-based list.

The thing for families to remember is that on lists such as these, differences between schools that are close together are essentially meaningless. Small or even irrelevant changes by the school or the magazine can move a college half a dozen places up or down.

Research indicates that graduates of highly selective schools do better economically, on average, though, so families with capable kids should at least consider higher-ranked schools, expensive though most of them are.

"Attendance of these selective private institutions not only gives you a leg up in the job market, but also into the next level of education, your chances of getting into the very best graduate and professional schools," Ehrenberg said.

But rather than worrying about whether a school is No. 2, 6 or 14 on the U.S. News list, families should focus on more traditional factors that will play a key role in the child's college experience: large school or small, urban or rural, coed or not. Is the school good in subjects the student expects to study? Are its offerings broad enough, in case the student changes majors? What about housing? Fraternities/sororities?

It's good to go to a selective school, but it's just as important to pick a school that's a good fit for the student. Don't let a few notches on some list cause you to forget that.

The College Lists

There are many ways to rank colleges. Here are the 10 highest ranking "best national universities" and the "best national liberal arts colleges," as listed by U.S. News & World Report magazine in its Aug. 30 issue; and the top 10 "values in private colleges" from Kiplinger's Personal Finance Magazine, which takes cost into account, in its September issue.

Best national universities

1. California Institute of Technology

2. Harvard University (Mass.)

3. Massachusetts Institute of Technology

4. Princeton University (N.J.)

4. Yale University (Conn.)

6. Stanford University (Calif.)

7. Duke University (N.C.)

7. Johns Hopkins University (Md.)

7. University of Pennsylvania

10. Columbia University (N.Y.)

Best national liberal arts colleges

1. Swarthmore College (Pa.)

2. Amherst College (Mass.)

3. Williams College (Mass.)

4. Wellesley College (Mass.)

5. Haverford College (Pa.)

5. Middlebury College (Vt.)

7. Pomona College (Calif.)

8. Carleton College (Minn.)

9. Bowdoin College (Maine)

10. Wesleyan University (Conn.)

Top values in private colleges

1. Rice University (Texas)

2. California Institute of Technology

3. Grinnell College (Iowa)

4. Washington and Lee University (Va.)

5. Cooper Union (N.Y.)

6. Amherst College (Mass.)

6. Stanford University (Calif.)

6. Swarthmore College (Pa.)

6. University of Chicago

10. Claremont McKenna College (Calif.)

NOTE: Schools with the same ranking were ties.

SOURCES: U.S. News & World Report, Kiplinger's Personal Finance Magazine