Inventory Fluctuations in the United States Since 1929

It has been known for a long time that inventory fluctuations are of great importance in business cycles. But inventory fluctuations are fundamentally a short-period phenomenon. Consequently, annual data may shed relatively little light on the nature of inventory fluctuations; most of the "action" may be played out within the year. For this reason, economists know precious little about inventory behavior before World War II. This paper seeks to lift this veil of ignorance in two ways. First,we create -- from some admittedly incomplete and imperfect data -- monthly time series on inventory holdings in manufacturing, durable manufacturing,and nondurable manufacturing. To our knowledge, these are the first such series ever made available.(The data are available on request.) Second,we apply to the prewar data certain statistical procedures and models that are in common use with postwar data. In this way, we can address the central issue of the paper: Has inventory behavior changed? While we do not wish to overstate the case, we were struck more by the similarities in inventory behavior between the prewar and postwar periods than by the differences. But the relevant stylized facts and regressing are displayed below, and each reader can make up his or her own mind.

Amniotic fluid from healthy term pregnancies does not harbor a detectable microbial community

Abstract Recent studies have conflicting data regarding the presence of intra-amniotic microbiota. Viral communities are increasingly recognized as important although overlooked components of the human microbiota. It is unknown if the developing fetus is exposed to a community of viruses (virome). Given the debate over the existence of an intra-amniotic microbial community and the importance of understanding how the infant gut is populated, we characterized the virome and bacterial microbiota of amniotic fluid from 24 uncomplicated term pregnancies using next-generation sequencing methods. Contrary to expectations, the bacterial microbiota of amniotic fluid was indistinguishable from contamination controls. Viral reads were sparse in the amniotic fluid, and we found no evidence of a core viral community across samples

Sticking it Out: Entrepreneurial Survival and Liquidity Constraints

This paper analyzes the role of liquidity constraints in the formation of new entrepreneurial enterprises. The basic empirical strategy is to determine whether an individual's wealth affects the probability of becoming an entrepreneur, and the conditional amounts of depreciable assets, ceteris paribus. If so, liquidity constraints are likely to be present. To be successful, such a research strategy requires a measure of asset variation that is both precisely measured and exogenous to the entrepreneurial decision. Our data are uniquely well-suited for this purpose. The sample consists of the 1981 and 1985 federal income tax returns of a group of people who received inheritances in 1982 and 1983, along with information on the size of those inheritances from a matched set of estate tax returns. Hence, we can examine how the exogenous receipt of capital affects the decision to become an entrepreneur and important financial characteristics of new enterprises. Our results suggest that the size of the inheritance has a substantial effect on the probability of becoming an entrepreneur, and that conditional on becoming an entrepreneur, the size of the inheritance has a statistically significant and quantitatively important effect on the amount of capital employed. These findings are consistent with the presence of liquidity constraints.

Horatio Alger Meets the Mobility Tables

The question of how entrepreneurship relates to income mobility is cogent given the current public debate about the sources of income inequality and mobility in United States society. We examine how experience with entrepreneurship has affected an individual's place in the earnings distribution. Our basic tack is to follow individuals' positions in the income distribution over time, and to see how their mobility (or lack thereof) was affected by involvement with entrepreneurship. Our main finding is that for low-income individuals there is some merit to the notion that the self-employed moved ahead in the earnings distribution relative to those who remained wage earners. On the other hand, for those at the upper end of the earnings distribution, those who became self-employed often advanced less in the earnings distribution than their salaried counterparts.

Minimizing Communication in Linear Algebra

In 1981 Hong and Kung proved a lower bound on the amount of communication needed to perform dense, matrix-multiplication using the conventional $O(n^3)$ algorithm, where the input matrices were too large to fit in the small, fast memory. In 2004 Irony, Toledo and Tiskin gave a new proof of this result and extended it to the parallel case. In both cases the lower bound may be expressed as $\Omega$(#arithmetic operations / $\sqrt{M}$), where M is the size of the fast memory (or local memory in the parallel case). Here we generalize these results to a much wider variety of algorithms, including LU factorization, Cholesky factorization, $LDL^T$ factorization, QR factorization, algorithms for eigenvalues and singular values, i.e., essentially all direct methods of linear algebra. The proof works for dense or sparse matrices, and for sequential or parallel algorithms. In addition to lower bounds on the amount of data moved (bandwidth) we get lower bounds on the number of messages required to move it (latency). We illustrate how to extend our lower bound technique to compositions of linear algebra operations (like computing powers of a matrix), to decide whether it is enough to call a sequence of simpler optimal algorithms (like matrix multiplication) to minimize communication, or if we can do better. We give examples of both. We also show how to extend our lower bounds to certain graph theoretic problems. We point out recently designed algorithms for dense LU, Cholesky, QR, eigenvalue and the SVD problems that attain these lower bounds; implementations of LU and QR show large speedups over conventional linear algebra algorithms in standard libraries like LAPACK and ScaLAPACK. Many open problems remain.Comment: 27 pages, 2 table

The Revenues-Expenditures Nexus: Evidence from Local Government Data

This paper examines the intertemporal linkages between local government expenditures and revenues. In the terminology that has become standard in the literature on vector autoregression analysis, the issue is whether revenues Granger-cause expenditures, or expenditures Granger-cause revenues. The main results that emerge from an analysis of fiscal data from 171 municipal governments over the period 1972-1980 are that: 1) one or two years are sufficient to summarize the relevant dynamic interrelationships; 2) there are important intertemporal linkages between expenditures, taxes and grants; and 3) past revenues help predict current expenditures, but past expenditures do not alter the future path of revenues. This last finding is contrary to results that have emerged from previous analyses of federal fiscal data, and hence suggests the need for additional research on the differences in the processes generating local and federal decisions.

Housing Tenure, Uncertainty, and Taxation

Modern empirical work on the choice between renting and owning focuses on the concept of the "user cost" of housing, which integrates into a single measure the various components of housing costs. The standard approach implicitly assumes that households know the user cost of housing with certainty. However, the ex post user cost measure exhibits substantial variability over time, and it is highly unlikely that individuals believe themselves able to forecast these fluctuations with certainty. In this paper, we construct and estimate a model of the tenure choice that explicitly allows for the effects of uncertainty. The results suggest that previous work which ignored uncertainty may have overstated the effects of the income tax system upon the tenure choice.

Health Insurance and the Supply of Entrepreneurs

Some commentators have suggested that the absence of portable health insurance impedes people from leaving their jobs to start new firms. We investigate this belief by comparing wage-earners who become self-employed during a given period of time with their counterparts who do not. By examining the impact of variables relating to the health insurance and health status of these workers and their families, we can infer whether the lack of health insurance portability affects the probability that they become self-employed. The evidence does not support the conjecture that the current health insurance system affects the propensity to become self-employed. Hence, whatever its other merits, there is no reason to believe that the introduction of universal health insurance would significantly enhance entrepreneurial activity.