Job Market Paper

The Impact of Supply Chain Disruptions: Evidence from the Japanese Tsunami (working paper)          December 2012

Despite attention in the media concerning the increasing number of international supply chain disruptions due to major natural disasters, little empirical evidence is available. Using, as a natural experiment, the sharp drop in Japanese exports of motor vehicles and parts to the USA after the Great Tohoku Earthquake and Tsunami 2011, the impact of the supply chain disruption on labour inputs adjustment in the US auto industry is estimated. Exploiting state-level variation in numbers of direct employment by Japanese auto makers and location of auto manufacturing factories, this paper identifies the adjustment among Japanese companies, their suppliers as well as their competitors based on the CPS and QWI data.
Notwithstanding significant losses of the Japanese firms' market share, I find that the disaster negatively affects only average monthly earnings of workers in Japanese assembly plants whereas their competitors do not seem to significantly increase any labour inputs in their assembly plants. Regarding changes in motor vehicle parts and accessories manufacturing, only production adjustment detected is in the counties where factories from the same auto companies are located. Moreover, other than a slight change in inventory management and sales incentive, there is no evidence of any adjustments on other margins of factors such as import substitution, or spikes in prices. These results suggest that the overall impact of this disaster on the US economy through the auto industry is rather small.

Completed Papers

Minimum Wage and Wage Inequality in Thailand: A Failed Instrument?                       April 2012

Most minimum wage literature in developing countries provides supporting evidence on its effectiveness in reducing wage inequality. Using the Thai Labor Force Survey from 1985 to 2009, I find rather mixed outcomes. Although minimum wage seems to help compress lower parts of wage distribution for employees in large businesses, the result is not robust. A compression effect vanishes during periods of declines in real minimum wage after the 1997 Asian financial crisis. In contrast with the lighthouse effect in Latin America, minimum wage in Thailand does not reduce informal wage inequality. Yet with available data, I cannot distinguish whether the high non-compliance rate among small businesses or a series of tiny increases in minimum wage is primarily responsible for such results.

Measuring Catastrophic Health Expenditures Using the Poverty Approach   Journal of Health Systems Research   Jul-Sep 2008
(In Thai, Co-author with Viroj NaRanong and Anchana NaRanong)

This paper uses household-specific poverty lines as a measure per household of catastrophic health expenditure in contrast to some studies which use arbitrary and universally cut-off shares (e.g., 10 percent) of health expenditures on household income as the main indicator of catastrophic health expenditure. Such indicators end up with counter-intuitive findings i.e. a substantial percentage of households in the richest quintile were found to be as prone to catastrophic health expenditures as those with lower income. Using the same data set, the study finds that, unlike households in the two lowest quintiles, it is extremely rare for those with higher-than-median incomes to have their post-health-expenditure income fall below the poverty line, a completely opposite result to those derived from the former indicator. Further, since the head count of health-related impoverished households is not sensitive for those already below the poverty line, the study proposes changes in the normalized poverty gap due to health expenditure, as a supplemental indicator for measuring an impact of health expenditure on poverty.

Research in Progress

Does Change in Compulsory School Law affect Schooling, Earnings and Health in Thailand?              Work-In-Progress

This paper estimates effects of series of changes in compulsory schooling law in Thailand on years of schooling, earnings and reported health status of cohorts subjected to such policy changes.