Product Substitutability and Productivity Dispersion

There are tremendous across-plant differences in measured productivity levels, even within narrowly defined industries. Most of the literature attempting to explain this heterogeneity has focused on technological (supply-side) factors. However, an industry's demand structure may also influence the shape of its plant-level productivity distribution. This paper explores the role of one important element of demand, product substitutability. The connection between substitutability and the productivity distribution is intuitively straightforward. When industry consumers can easily switch between suppliers, it is more difficult for relatively inefficient (high-cost) producers to profitably operate. Increases in product substitutability truncate the productivity distribution from below, implying less productivity dispersion and higher average productivity levels in high-substitutability industries. I demonstrate this mechanism in a simple industry equilibrium model, and then test it empirically using plant-level data from U.S. manufacturing industries. I find that as predicted, product substitutability measured in several ways is negatively related to within-industry productivity dispersion and positively related to industries' median productivity levels.

Cementing Relationships: Vertical Integration, Foreclosure, Productivity, and Prices

This paper empirically investigates the possible market power effects of vertical integration proposed in the theoretical literature on vertical foreclosure. It uses a rich data set of cement and ready-mixed concrete plants that spans several decades to perform a detailed case study. There is little evidence that foreclosure is quantitatively important in these industries. Instead, prices fall, quantities rise, and entry rates remain unchanged when markets become more integrated. These patterns are consistent, however, with an alternative efficiency-based mechanism. Namely, higher productivity producers are more likely to vertically integrate and are also larger, more likely to survive, and charge lower prices. We find evidence that integrated producers' productivity advantage is tied to improved logistics coordination afforded by large local concrete operations. Interestingly, this benefit is not due to firms' vertical structures per se: non-vertical firms with large local concrete operations have similarly high productivity levels.

How do Incumbents Respond to the Threat of Entry? Evidence from the Major Airlines

We examine how incumbents respond to the threat of entry by competitors (as distinct from how they respond to actual entry). We look specifically at passenger airlines, using the evolution of Southwest Airlines’ route network to identify particular routes where the probability of future entry rises abruptly. We find incumbents cut fares significantly when threatened by Southwest’s entry. Over half of Southwest’s total impact on incumbent fares occurs before Southwest starts flying. These cuts are only on threatened routes, not those out of non-Southwest competing airports. The evidence on whether incumbents are seeking to deter or accommodate entry is mixed.

Product Differentiation, Search Costs, and Competition in the Mutual Fund Industry: A Case Study of the S&P 500 Index Funds

Two salient features of the competitive structure of the U.S. mutual fund industry are the large number of funds and the sizeable dispersion in the fees funds charge investors, even within narrow asset classes. Portfolio financial performance differences alone do not seem able to fully explain these features. We investigate whether non-portfolio fund differentiation and information/search frictions also play a role in creating these observed industry characteristics. We focus on their impact in a case study of the retail S&P 500 index funds sector. We find that fund proliferation and price dispersion also exist in this sector, despite the funds' financial homogeneity. Furthermore, there was a marked shift in sector assets to more expensive (often newly entered) funds throughout our sample period. Our analysis indicates that these observations are consistent with the presence of both non-portfolio differentiation and information/search frictions. Structural estimation of a novel search-over-differentiated-products model reveals that reasonable magnitudes of investor search costs can explain the considerable price dispersion in the sector, and consumers seem to value funds'' observable attributes such as fund age and the number of other funds in the same fund family in largely plausible ways. The results also suggest that the substantial increase in mutual fund market participation observed during our sample, and the corresponding purchase decisions of novice investors, drove the shift in assets toward more expensive funds. We also find evidence consistent with the presence of switching costs, as distinct from search costs. Using structural estimates of demand parameters and search costs, we investigate the possibility that there are too many sector funds from a social welfare standpoint. The results of this exercise indicate that restricting entry would yield nontrivial gains from reduced search costs and productivity gains from scale economies, but these may be counterbalanced by losses from increased market power and reduced product variety.

Market Distortions when Agents are Better Informed: The Value of Information in Real Estate Transactions

Agents are often better informed than the clients who hire them and may exploit this informational advantage. Real-estate agents, who know much more about the housing market than the typical homeowner, are one example. Because real estate agents receive only a small share of the incremental profit when a house sells for a higher value, there is an incentive for them to convince their clients to sell their houses too cheaply and too quickly. We test these predictions by comparing home sales in which real estate agents are hired by others to sell a home to instances in which a real estate agent sells his or her own home. In the former case, the agent has distorted incentives; in the latter case, the agent wants to pursue the first-best. Consistent with the theory, we find homes owned by real estate agents sell for about 3.7 percent more than other houses and stay on the market about 9.5 days longer, even after controlling for a wide range of housing characteristics. Situations in which the agent's informational advantage is larger lead to even greater distortions.

Reallocation, Firm Turnover, and Efficiency: Selection on Productivity or Profitability?

There is considerable evidence that producer-level churning contributes substantially to aggregate (industry) productivity growth, as more productive businesses displace less productive ones. However, this research has been limited by the fact that producer-level prices are typically unobserved; thus within-industry price differences are embodied in productivity measures. If prices reflect idiosyncratic demand or market power shifts, high "productivity" businesses may not be particularly efficient, and the literature's findings might be better interpreted as evidence of entering businesses displacing less profitable, but not necessarily less productive, exiting businesses. In this paper, we investigate the nature of selection and productivity growth using data from industries where we observe producer-level quantities and prices separately. We show there are important differences between revenue and physical productivity. A key dissimilarity is that physical productivity is inversely correlated with plant-level prices while revenue productivity is positively correlated with prices. This implies that previous work linking (revenue-based) productivity to survival has confounded the separate and opposing effects of technical efficiency and demand on survival, understating the true impacts of both. We further show that young producers charge lower prices than incumbents, and as such the literature understates the productivity advantage of new producers and the contribution of entry to aggregate productivity growth.

Simultaneous Bilateral Total Knee Arthroplasty and the Effects of Physical Therapy in the Outpatient Setting: A Case Study.

Background and Purpose: A bilateral total knee arthroplasty (TKA) is a surgical procedure that has seen success in managing end-stage osteoarthritis of the knee joint. This case study evaluates the usefulness of physical therapy following bilateral TKA and deliberates the outcomes the patient experienced. Case Description: The patient was a 62-year-old male who received postoperative physical therapy in an outpatient orthopedic clinic for a total of 8 weeks. The patient demonstrated decreased bilateral knee range of motion (ROM), decreased bilateral gross lower extremity (LE) strength, increased pain and swelling in both knees, and decreased endurance for ambulation. Intervention: Therapy provided to the patient emphasized the use of traditional TKA exercises as well as functional exercises. These exercises were used to assist in increasing bilateral knee ROM, bilateral knee strength, and the overall functional mobility of the patient. Outcomes: Throughout the course of treatment, the patient was able to increase his knee ROM bilaterally, LE strength, decrease his pain and swelling, and increase his endurance for ambulation. Discussion: The patient responded favorably to treatment, and many of the goals created were achieved. A clinical practice guideline on the management of total knee arthroplasty was recently released during the writing of this case study, and it can be referenced for the most current research on the examination and treatment for patients with total knee replacement