PEOPLE RESPOND TO INCENTIVES. My students have heard it from me again, and again, and again: a shortage is the consequence of a price at which desired consumption exceeds available production. Highered Intelligence gets it, and provides a link to an essay by economics professor Michael Podgursky that spells it out.

"School districts must also develop more efficient, market-oriented compensation policies. Unfortunately, nearly all of them still determine teacher pay according to salary schedules based on years of teaching experience and graduate education credit hours. These schedules apply to all teachers—from kindergarten to high school physics—regardless of subject expertise, school conditions, or individual effectiveness. Such rigid schedules have two unfortunate consequences. First, they produce shortages. Kindergarten teachers and high school physics teachers are both important, but their alternative earnings opportunities differ greatly and the teacher-pay system must take account of that. Imagine how well university business and engineering schools would be staffed if they paid faculty salaries no higher than the sociology department.

"These rigid schedules also guarantee that poor children will get weaker teachers. School working conditions differ, and schools with many poor and minority students are often located in tough or inconvenient neighborhoods. Many teachers use their seniority to transfer to more pleasant and accessible environs. By paying the same rates in every school, these salary schedules make it harder for inner city schools to get the most experienced instructors. The military has long recognized the need for "hazardous duty pay." Public schools need to do something similar."

Let me add one observation that Professor Podgursky has not given you: the universities of the United States are stronger precisely because the British, and possibly other European universities, have the same pay packets for professors of comparable seniority, irrespective of field.