A、It does research among small numbers of graduates. B、It ignores schools unfairly affected by local job markets. C、It overstate

Too many degrees are a waste of money. The return on higher education would be much better if college were cheaper. There is no simple answer to the question "Is college worth it?". Some degrees pay for themselves; others don’t [22]College graduates aged 25 to 32 who are working full time earn about $17.500 more annually than their peers who have only a high school diploma, according to the Pew Research Centre, a think-tank. But not all degrees are equally useful. And given how much they cost—a residential four-year degree can set you back as much as $60,000 a year—many students end up worse off than if they had started working at 18.
    PayScale, a research firm, has gathered data on the graduates of more than 900 universities and colleges, asking them what they studied and how much they now earn. The company then factors in the cost of a degree, after financial aid. From this, PayScale estimates the financial returns of many different types of degree. [23]Unsurprisingly, engineering is a good bet wherever you study it. An engineering graduate from the University of California, Berkeley can expect to be nearly $l.lm better off after 20 years than someone who never went to college. Arts and humanities courses are much more varied. All doubtlessly nourish the soul, but not all fatten the wallet. Of the 153 arts degrees in the study, 18 offered returns worse than zero.
    Colleges that score badly will no doubt grumble that PayScal’s rankings are based on relatively small numbers of graduates from each institution. Some schools are unfairly affected by the local job market. And poor colleges will look worse than rich ones that offer lots of financial aid, since reducing the cost of a degree raises its return. All these are true. [24]But overall, the PayScale study surely overstates the financial value of a college education. It does not compare graduates’ earnings to what they would have earned, had they skipped college. It compares their earnings to those of people who did not go to college, many of whom did not go because they were not clever enough to get in. Thus, some of the premium that graduates earn simply reflects the fact that they are, on average, more intelligent than non-graduates.
     [25]For all their flaws, studies like PayScale’s help would-be students (and their parents’) make more informed choices. As Americans start to realise how much a bad choice can hurt them, they will demand to be more informed. Some colleges are providing it, pushed by the federal government. For example, the University of Texas recently launched a website showing how much its graduates earn and owe after five years.
22. What did the Pew Research Centre find?
23. According to PayScale, what subject is good in terms of returns?
24. According to the speaker, what is the real shortcoming of the PayScale study?
25. According to the speaker, what is the benefit brought by studies like Payscale’s?