Extensive and Intensive Investment over the Business Cycle
美国企业的投资对托宾Q的反应不对称：老企业（集约投资）对Q反应为负，新企业（广延投资）对Q反应为正且富有弹性，这源于新旧技术兼容成本差异。
Investment of U.S. firms responds asymmetrically to Tobin's Q: Investment of established firms -- `intensive' investment -- reacts negatively to Q whereas investment of new firms -- `extensive' investment -- responds positively and elastically to Q. This asymmetry, we argue, reflects a difference between established and new firms in the cost of adopting new technologies. A fall in the compatibility of new capital with old capital raises measured Q and reduces the incentive of established firms to invest. New firms do not face such compatibility costs and step up their investment in response to the rise in Q. A composite-capital version of the model fits the data well using aggregates since 1900 and our new database of firm-level Qs that extend back to 1920.