America's most prestigious universities have just gained a new argument to justify skyrocketing tuitions, thanks to research from one of their own professors.

美國最富盛名的大學剛剛獲得了一個證明不斷飆升的學費合理的新理由，這要得益于一名他們自己教授的研究結果。

In a new paper, Caroline Hoxby, a Stanford (and formerly Harvard) economist who specializes in educational issues, tackles a question dogging many parents of college-age children: Why it seems so much harder for their offspring to get into a good college than it was for them. A big part of the answer, she concludes, is that the market for education has gone global. That means the pool of applicants to the best universities has expanded to include students from many different backgrounds and locales--students who might once have aspired mainly to local schools.

斯坦福大學(Stanford)經濟學家卡羅琳•霍克斯比(Caroline Hoxby)在一篇新論文中探討了令很多大學生家長感到困惑的一個問題：為什么和他們當年相比，現在孩子上一所好大學會困難得多？霍克斯比曾在哈佛大學執教，教育問題是她的研究方向。霍克斯比認為，很大一部分原因是，教育市場正走向全球化。這意味著申請最優秀大學的生源范圍擴大，如今包括了很多不同背景和地區的學生，而這些學生可能之前基本都想著上當地學校。

The phenomenon, she notes, has boosted selectivity only at the top institutions. In 2007, the average student accepted by the most selective 5% of colleges scored in the 98th percentile on entrance exams, compared to an average score in the 90th percentile in 1962. Meanwhile, as more students have set their sights higher, other colleges have become less selective. In fact, getting accepted at any college has actually become easier, Hoxby argues, as the total number of freshman seats has grown faster than the number of prepared high-school graduates.

霍克斯比說，這一現象只令上頂尖大學變得更困難。2007年，美國最頂級的5%大學的錄取新生的平均入學考試成績是排在所有考生的前2%，而1962年這一平均成績是排在所有考生的前10%。與此同時，隨著更多的學生眼光提高，其他學校挑選生源的選擇余地下降。霍克斯比說，現在學生要被大學錄取已經變得更加容易，因為大學的招生計劃總數的增長速度要快于有志于讀大學的高中畢業生數量。