Question about University rankings (please help)

In the far future after I complete a Bachelors I plan on going to a graduate school to study Physics and Political Science.

I hope to get accepted into a very prestigious school and I was researching the top ranked schools in America and considered the ones that had an acceptance rate above 20% because it doesn’t seem realistic to attend a school that has around 2-7% acceptance rates.

The problem I ran into was that their was 2 different rankings which are “Global University Rankings” and “National University Rankings”, at first I thought the only difference between the 2 was that Global Rankings applies to all schools in the world and National Rankings applies to all schools in America.

But it seems like that’s not the case because if you look at the Global Rankings and only consider the schools in America, the list is still very different from the National Rankings so I’m a little confused as to which ranking system I should trust, the links to the sources are below.
http://www.usnews.com/education/best-global-universities/search?region=&country=united-states&subject=&name=
http://colleges.usnews.rankingsandreviews.com/best-colleges/rankings/national-universities/data

Any advice?

Here are Global Rankings with 20%+ Acceptance:

1-Uni Michigan
2-Uni Washington
3-UC San Diego
4-Uni Wisconsin Madison
5-UC Santa Barbara

Here are National Rankings with 20%+ Acceptance:

1-Uni Notre Dame
2-Emory Uni
3-Uni Virginia
4-Carnegie Mellon Uni
5-Wake Forest Uni

They use very different criteria.

Which should you trust for what? Are you looking to apply for undergrad or grad school?

Personally, I’m of the opinion that you shouldn’t blindly trust either and explore each school.

Here are the criteria for the “Best Global Universities” rankings:
http://www.usnews.com/education/best-global-universities/articles/methodology

Here are the criteria for the “Best [American] Colleges” rankings:
http://www.usnews.com/education/best-colleges/articles/2014/09/08/best-colleges-ranking-criteria-and-weights

Notice the emphasis in the “Global” ranking on publications and citations, which are not considered in the “Best Colleges” ranking. The latter looks at other factors the “Global” ranking does not, such as undergraduate admissions selectivity, class sizes, and college graduation rates. The “Global” ranking probably is more appropriate for prospective graduate students. Although many HS students may care about research quality and productivity, the top scholars who boost “Global” scores in those areas won’t necessarily teach too many undergraduate classes. They may at some colleges. This is an example of why you do need to “explore each school” (although you may want to consult these or other rankings early in the process, to help discover schools and build an appropriate first-pass application list before you explore them in greater depth.)

You want to go to graduate school in physics AND political science??? Odd?

I would say to find some additional ranking organizations as well. Forbes is one. There is another more international ranking system that escapes me right now…

For my kids we looked into 3 or 4 and made our own weighted average based upon the detail of the ranking criteria.

US News, for example, uses spending by the school as a measure of ‘better’. So the exact same school in California would score higher than one in Nevada simply because the cost of living is higher there. (higher professor salaries)

By not having considered National Liberal Arts Colleges as of this point, either of the rankings you have viewed are insufficient if you want to explore all of your options for aligning your choice of an undergraduate college with your stated goals. For example, five of the top eight colleges with respect to producing future PhDs in science and engineering are LACs. I’d go further to state that the Global University rankings are probably a counterproductive reference, as their emphasis appears to have little to do with undergraduate education.

(National Science Foundation; normalized for bachelor’s awarded.)