Knowledge that Transforms

In this paper we discuss several statistical techniques which may be used to test the validity of a possibly non-linear and multivariate regression model, using the information provided by estimating one or more alternative models on the same set of data. We first exposit, from a different perspective, the tests proposed by us in Davidson and MacKinnon (1981a), and discuss modified versions of these tests and extensions of them to the multivariate case. We then prove that all these tests, and also the tests previously proposed by Pesaran (1974) and Pesaran and Deaton (1978), based on the work of Cox (1961, 1962), are asymptotically equivalent under certain conditions. Finally, we present the results of a sampling experiment which shows that different tests can behave quite differently in small samples.

This paper extends the seminal work of Akerlof, and Salop and Stiglitz in two directions: (i) the sellers can select both the selling prices and quality levels of their good, and (ii) the buyers can acquire price/quality information about individual sellers at a cost. We observe multiple price/quality combinations in equilibrium, which depend upon the distribution of information costs of consumers and upon whether quality, or price, or both are costly observable. Welfare comparisons of equilibrium are considered. We show that welfare will be greater when price advertising is permitted.

Since 1975 labour slack has been unusually high in the OECD countries, and yet inflation has not diminished. The less favourable mix of unemployment and rate of change of inflation (which we call stagflation) is explained by a fall in the feasible rate of growth of real wages unmatched by a reduction in the constant term in Phillips curve. To investigate this mechanism, conventional wage and price equations are estimated for 19 countries and then used for simulation. Stagflation has been caused in roughly equal amounts by rising relative import prices and by the fall in the rate of productivity growth. In the basic model the Phillips curve is assumed not to adapt to falls in feasible real wage growth, but in a final section an adaptive wage equation is estimated, which confirms that the process of adaptation is slow.

The paper uses two approaches to study whether aggregate fluctuations in employment and unemployment may be explained within a market clearing framework as intertemporal substitution in labour supply. First, log-linear equations for labour supply and unemployment are estimated using a forecasting model to measure wage and price expectations. Second, a utility function is used to derive and estimate an equation for labour supply as a function of the current real wage and consumption. The influence of expected future real wages and interest rates is captured by the consumption variable. The empirical results do not support the intertemporal substitution model.

It has been alleged that, contrary to the assumptions in Pareto's Manual, the ability to compare first-differences of utility implies cardinality. It is shown here that the validity of this theorem hinges critically on the framework of analysis. In the framework of the thirties it is valid because of the implicit use of an ‘unrestricted domain’ assumption. In the modern choice-theoretic context it is not in general true but it becomes valid if utility functions are continuous and are defined on a connected topological space.

Alternative methods of computing estimates of inequality measures from grouped data are critically examined in terms of their theoretical and empirical properties. The use of a simple “split-histogram” technique of interpolation is explained and supported. Theoretical and empirical support is also provided for the “⅓/⅔ rule”—a simple computational procedure for a point estimate of an inequality measure derived from its standard grouping bounds.

This paper provides a theoretical synthesis of recent discussions of "learning by doing" and "investment in training" as alternative forms of human capital accumulation. These theoretical notions relate to essentially different phenomena; in particular, pace Becker and Mincer, "investment in training" does not completely encompass "learning by doing". The paper then develops a model in which human capital accumulation occurs via both "training" and "learning by doing". The joint training-learning model, since it is more general then "pure" models in which all accumulation occurs via either training or learning, avoids certain restrictive and seemingly implausible implications of either kind of "pure" model. However, the joint model also has implications that, while compatible with stylized facts about the life cycle, are sharper than those of either kind of pure model. (For example, the joint model implies that market time and earnings must rise early in the life cycle, while neither pure model without "corners" does so.) Finally, the notion of learning by doing provides a rationale for an empirical finding that has recently received attention, to the effect that the rate of depreciation of human capital is not constant, but rather depends on the extent to which it is used in market activities.

This paper is concerned with measuring the true impact of certain human capital variables on an individual's occupational position. The particular variables which are analysed are training, qualifications and spells of sickness and unemployment. The longitudinal nature of the data enables us to control for all relevant individual attributes which remain fixed over the period of the sample. This is vitally important because these attributes are strongly correlated with the variables of interest and would seriously corrupt estimates derived from a single cross-section. A method of generating consistent estimates (as N → ∞, T fixed) for a dynamic model with fixed effects is also illustrated.

This paper studies a central aspect of optimal income taxation as modelled in Mirrlees' original paper on the topic (identical leisure/consumption preferences, qualitatively homogeneous "skills" in production), namely, whether given concave utilitarianism alone the optimal marginal income tax will be non-negative. A well-known positive answer to this question (in weak inequality form) was given in the said paper which, however, we show requires additive separability of individual utility (in the ordinal and cardinal senses). Our main result here is to derive the required (strict) positivity of the marginal tax under weak conditions, slightly wider than noninferiority of consumption and leisure, with preferences otherwise arbitrary.

This paper examines the relative importance of timing and persistence elements in explaining cyclical fluctuations in labour supply. Data from the natural experiment provided by World War II and cross-sectional data on American local labour markets, as well as aggregate time-series data are used in the empirical work. We find little evidence that timing effects play an important role in labour market dynamics. The evidence suggests that views emphasizing persistence are more accurate, and that previous employment tends to raise the probability of subsequent employment.