Productivity Differences Across Employers: The Roles of Employer Size, Age, and Human Capital
利用美国数据，研究雇主规模、年龄和人力资本如何解释企业间的生产率差异，发现人力资本是重要因素。
Productivity Differences across Employers: The Roles of Employer Size, Age, and Human Capital by John C. Haltiwanger, Julia I. Lane and James Spletzer. Published in volume 89, issue 2, pages 94-98 of American Economic Review, May 1999