Deconstructing a Mortgage Meltdown: A Methodology for Decomposing Underwriting Quality

Technical progress in originating and pricing mortgages has enabled a trend since 1979 toward relaxed credit standards for lending, reflected in rising foreclosure rates. We develop a methodology for decomposing the trend in mortgage performance into a part due to economic conditions and a part due to underwriting changes, and provide natural metrics or indices of underwriting quality and economic conditions. The recent mortgage debacle can be attributed about equally to each factor. Important underwriting characteristics were eased in the 1990s, but the negative effects of lower standards were masked by strong local and national economic conditions. After 2002, there was little change in observable loan characteristics, but loan performance still eroded, even after controlling for the economic environment. Our evidence suggests that erosion after 2002 must have arisen from underwriting covariates that are unobservable to investors, consistent with the hypothesis that moral hazard in “nonagency” securitizations caused underwriting risks to be mispriced.     

Two Theorems on Generalized Diminishing Returns and their Applications to Economic Analysis*

Under certain weak assumptions such as free disposal and non-satiety, it is shown that the concavity of utility and of technology implies that the maximum value of the set of all attainable programmes is a concave function of the initial capital stocks. For time-independent problems, this implies that along an optimal path, as a capital stock is accumulated, its shadow price falls. The usefulness of the theorems is demonstrated in a number of examples, including Kemp's cake-eating problem and Forster's pollution-control problem.     

Assessing the Performance of Business Unit Managers

Using a sample of 140 managers, we investigate the use of various performance metrics in determining the periodic assessment, bonus decisions, and career paths of business unit managers. We show that the weight on accounting return measures is associated with the authority of these managers, and we document that both disaggregated measures (expenses and revenues), and nonfinancial measures play a greater role as interdependencies between business units increase. The results suggest separate and distinct roles for different types of performance measures. Accounting return measures are used to create the proper incentives for managers with greater authority, while disaggregated and nonfinancial measures are employed in response to interdependencies.     

From Wall Street to Main Street: The Impact of the Financial Crisis on Consumer Credit Supply

How did the collapse of the asset‐backed securities (ABS) market during the 2007 to 2009 financial crisis affect the supply of credit to the broader economy? Using new data on the U.S. credit union industry, we find that ABS‐related losses are associated with a large contraction in the supply of credit to consumers, especially among those credit unions that began the crisis with weaker capitalization. We also find that this credit supply shock restricted the availability of mortgage and automobile credit. These results show how movements in the prices of financial assets can affect the real economy.     

The Exchange Rate in the Presence of Transaction Costs: Implications for Tests of Purchasing Power Parity

With transaction costs for trading goods, the nominal exchange rate moves within a band around the nominal purchasing power parity (PPP) value. We model the behavior of the band and of the exchange rate within the band. The model explains why there are below-unity slope coefficients in regression tests of PPP, and why these increase toward unity under hyperinflation or with low-frequency data. Our results are independent of the presence of nontraded goods in the economy.     

COMPARING PER CAPITA INCOME IN THE HELLENISTIC WORLD: THE CASE OF MESOPOTAMIA

Until quite recently, GDP growth between ca. 1 ce and the late Middle Ages was considered non‐existent or even negative. Recently, largely on account of increasing interest in historical national accounting, the late‐medieval figures have been revised upward, in line with an upward adjustment in the estimated shares of manufacturing and pasture. Leaving GDPs dating from the ancient world unaltered would consequently generate figures indicating increased economic growth during the first millennium ce . A considerable number of studies of the late‐medieval period (the object of increasing attention on the part of specialists in early economic history) have caused estimates for the ancient one to be revised upwards, essentially leaving estimates of the changes in economic development over time unaltered. These studies, however, have focused on the Roman Empire and Italia while there is a consensus in the literature that it was quite unrepresentative of all ancient societies with its relatively high share of GDP from the manufacturing sector of the economy. We therefore estimate a new per capita income for another contemporary agrarian society: ancient Mesopotamia. In addition, by examining manufacturing and pasture—the two main reasons for higher income which have been identified in the literature—we have found a tentative explanation for the fact that ancient Mesopotamia's per capita income deviated from that of Rome.     

GROWTH,RENEWABLES, AND THE OPTIMAL CARBON TAX

Optimal climate policy is investigated in a Ramsey growth model of the global economy with exhaustible oil reserves, an infinitely elastic supply of renewables, stock‐dependent oil extraction costs, and convex climate damages. Four regimes can occur, depending on the initial social cost of oil being larger or smaller than that of renewables and depending on the initial oil stock being large or small. We also offer some policy simulations for the first and second regime, which illustrate that with a lower discount rate more oil is left in situ and renewables are phased in more quickly. We identify the conditions under which the optimal carbon tax rises or decreases. Subsidizing renewables (without a carbon tax) induces more oil to be left in situ and a quicker phasing in of renewables, but oil is depleted more rapidly initially. The net effect on global warming is ambiguous.