Mankiw的教科書是全球最多大學選用的基礎經濟學教科書，從這個層面說他絕對是目前最具影響力的經濟學家，其思想直接影響到莘莘學子。
講這麼多讚譽的話，其實是想帶出Mankiw 教授今日在New York Times的撰文《When the Scientist Is Also a Philosopher》，「教導」大家做經濟學人應該有Philosopher的一面。
Do you want to know a dirty little secret of economists who give policy advice? When we do so, we are often speaking not just as economic scientists, but also as political philosophers. Our recommendations are based not only on our understanding of how the world works, but also on our judgments about what makes a good society.
The necessity of political philosophy arises because most policies are good for some people and bad for others. For example, an increase in the minimum wage, as proposed by President Obama, may raise incomes for some low-wage workers, but it will cause some businesses to make smaller profits, some customers to pay more and some workers to lose their jobs.
唔記得同你講，Mankiw教授一向都是極度反對美國調高最低工資的，早前他就聯署左一封有多達500名頂級經濟學合簽的反對加最低工資的公開信，所以文中提最低工資一事亦為意料之內。
在最低工資的爭論中，最大的爭議點當然是，提高最低工資是否對社會整體有利。這一向是經濟學者對政策研究的方向，Maximizing Social Welfare。
過往幾十年，在自由經濟學派的理論領導下，學界對最低工資都相當有介心，原因是在基礎Supply Demand Analysis下，干預市場價格必然會帶來負面的Social Welfare 影響。
不過，這以已經是歷史了。近年不少實證研究，都開始對這個不可干擾市場價格的金科玉律提出質疑，不少研究指出提高最低工資後並無令相關地區的總體失業率顯着上升，反而拎最低工資的人的生活水平可得以改善。就算是在青年失業率上，最低工資調高都只是帶來輕微的上升。這樣說，近年支持最低工資的一派，氣勢不錯。（註1）
今番反最低工資的領軍人物Mankiw出文反擊，本著期待的心情看文。Mankiw 一開始就先解讀上述的maximizing social wefare方法，其實是一種Utilitarian的看法。
To strike this balance, many economists think in terms of a “social welfare function” that aggregates individuals’ well-being into a summary measure. This approach dates back to the utilitarian philosophers of the 19th century, such as Jeremy Bentham and John Stuart Mill. The utilitarians suggested that each person in society receives a certain amount of happiness, or “utility,” from an allocation of society’s resources. The job of policy makers, they argued, is to do their best to maximize the total utility of everyone in society. According to utilitarians, taking a dollar from Peter and giving it to Paul is justified if Peter’s decrease in utility is smaller than Paul’s increase, as would plausibly be the case if Peter is richer than Paul.
那教請問教授這方法有甚麼建議？
So, what is the alternative? At the very least, a large dose of humility is in order. ……
……In some ways, economics is like medicine two centuries ago. If you were ill at the beginning of the 19th century, a physician was your best bet, but his knowledge was so rudimentary that his remedies could easily make things worse rather than better. And so it is with economics today. That is why we economists should be sure to apply the principle “first, do no harm.”…..
…….As I see it, the minimum wage and the Affordable Care Act are cases in point. Noble as they are in aspiration, they fail the do-no-harm test. An increase in the minimum wage would disrupt some deals that workers and employers have made voluntarily. ……. these policies were canceled because they deviated from lawmakers’ notion of the ideal.
But keep in mind that in making that judgment, they [economists favoring minimum wage increase] are relying on forecasts from a far-from-perfect science, as well as a healthy dose of their own political philosophy.
What the ____!? Mankiw基本上同我地講，經濟學者過去的預測一向唔太準確，所以對於他們的意見唔可以盡信，更重要的是，如果對政策效果有疑問，就應該本着「do no harm」的原則，將所有可能有負面影響的政策否決。
我好難相信，這位經濟學中極有影響力的學者會用建議大家用這樣的理由，去推翻一個經濟政策，更不要說他的教科書很大程度上就是教大家以Utilitarianism的角度，去作政策分析。Do No Harm原則是必要的，但在衡量政策上現有證據作考慮，我們無可能有完美證據，至少短期內不會有。因為有可能有負面影響，證據可能不足就否決經濟政策，這不是一個好的經濟政策方法。
註1： 頭盔，我不是想講目前所有研究都指出提高最低工資無負面影響，更是有為數不少的研究認為最低工資對社會整體有負面影響。我所描述的情況是近年認為最低工資無害的研究愈來愈多，令這派的氣勢較強。
延讀： http://www.econlib.org/library/Columns/y2014/Murphyminimumwage.html
