Sounds and Fury

我發現我之前在部落格寫的關於美國不平等的筆記都有點混亂。
（之前的討論見此一、二、三、四）

最近花了些時間在經濟學家期刊中打轉，這裡先對造成美國不平等的原因作簡單整理。


主要幾個原因包括貿易、偏向技術的科技變革、移民，以及所謂制度面的解釋：這最常被舉出的就是工會組織率降低和最低工資的停滯---而這恰好是最近美國通過的兩大法案改革。

貿易的效果現在越來越多經濟學家質疑，如國際貿易大師J. Baghwati說：The culprit is not globalisation but labour-saving technical change that puts pressure on the wages of the unskilled. Technical change prompts continual economies in the use of unskilled labour.


這個科技變遷因素大概是不少經濟學家都同意的結果。（例如這篇新文章：
David H. Autor, Lawrence F. Katz, and Melissa S. Kearney, January 2006. AER）


但是也有人反對
Paul Krugman
I think it's really important to realize that we have only a modest amount of direct evidence that technological change is driving increased income inequality. That is, while there have been a few studies showing some connection between increased use of IT and changes in the wage structure, very little of the conventional wisdom that technology is the culpritis based on those studies.
So why is technology given the credit? Basically because it's the residual category - and as Bob Solow said about the role of technology in growth, the residual is the measure of our ignorance. We estimate the effects ofthe stuff whose effects we know how to measure - taxes and globalization, mainly - and then attribute the rest to technology.
The point is that it's all too possible that we're attributing to technology rising inequality that may be largely due to hard-to-quantify political and institutional change.


著名勞工經濟學家David Card
It seemed like analysts were saying: “It's all just SBTC. There's nothing more to say.” We wanted to point out that there are many, many puzzles that SBTC can't explain and that people should be working on. 因為

A key problem for the SBTC hypothesis is that wage inequality stabilized in the 1990s despite continuing advances in computer technology; SBTC also fails to explain the evolution of other dimensions of wage inequality, including the gender and racial wage gaps and the age gradient in the return to education.
Skill-Biased Technological Change and Rising Wage Inequality: Some Problems and Puzzles

David Card and John E. DiNardo
Journal of Labor Economics, 2002, vol. 20, no. 4


比較有趣的是最低工資和工會的效果。
就工會來說，David Card的研究指出，de-unionization explains between 10 and 20 percent of the rise in wage inequality for men over the past 30 years
---“Falling Union Membership and Rising Wage Inequality: What's the Connection?”


就最低工資的效果來說，這幾篇著名論文發現：
DiNardo, J., Fortin, N. M. and Lemieux, T. (1996). 'Labor market institutions and the distribution of wages, 1973–1992', Econometrica, vol. 64(5), pp. 1001–44.
They hold minimum wages responsible for 25% of the increase in wage dispersion during the 1980s

Lee, David S. 1999. “Wage Inequality in the United States During the 1980s: Rising Dispersion or Falling Minimum Wage?” Quarterly Journal of Economics, vol. 114, 3, August, 977-1023.
"almost all of the growth in the wage gap between the tenth and fiftieth percentile is attributable to the erosion of the real value of the federal minimum during the 1980s."

Coen N. Teulings (2003) “The contribution of minimum wages to increasing wage inequality”, The Economic Journal 113 (490), 801–833.
"minimum wages can explain the whole increase in wage inequality in the lower half of the wage distribution during the 1980s."


Brad Delong不太相信制度可以解釋很多，但是還是有部分解釋力。
My sense (and it is just a guess) is that declining unionization and union power might account for perhaps a fifth of the widening in income inequality; that reductions in the value of the minimum wage might account for a tenth; and that legal changes that have shifted the balance of power within the corporation toward CEOs might account for another tenth.