How Productive is Public Capital? A Meta-Analysis

The paper analyzes the contribution of public capital to private output using several metaanalytical techniques. Both fixed and random effects models are estimated by Weighted Least Squares. Sample overlap across studies is explicitly controlled for by employing a `full' Generalized Least Squares estimator. The weighted average output elasticity of public capital amounts to 0.08 after correcting for publication bias. A substantial part of the heterogeneity across studies is explained by study design parameters, such as econometric specification, estimation technique, empirical model, type of public capital, and level of aggregation of public capital data. The large elasticities of public capital found in the early literature seem to be caused by either unidentified (but present) cointegrating relationships or spurious relationships in national time series.public capital;infrastructure;public investment;meta-analysis;meta-regression analysis;publication bias

Output Dynamics, Technology, and Public Investment

The paper studies the dynamic output effects of public infrastructure investment in a small open economy. We develop an overlapping generations model that includes a production externality of public capital and a wealth effect on labor supply. Public capital enters the firm's production function under various technological scenarios. We show that if factors of production are gross complements and public capital is Solow neutral, which is the empirically plausible case, the long-run output multiplier falls short of its Hicks-neutral value. The way in which public capital augments factor productivity crucially affects the dynamics of private capital and net foreign assets, but yields qualitatively similar output dynamics. In contrast to conventional results obtained from hysteretic models, we find non-monotonic output dynamics of a public investment impulse in the non-hysteretic model. Schmitt-Grohe and Uribe's (2003) finding of identical impulse responses across the two model types is thus not robust to the inclusion of spillovers of public capital.Infrastructure capital;public investment;fiscal policy;output multipliers;transitional dynamics;technology

Gambling as a teaching aid in the introductory physics laboratory

Dice throwing is used to illustrate relevant concepts of the statistical theory of uncertainties, in particular the meaning of a limiting distribution, the standard deviation, and the standard deviation of the mean. It is an important part in a sequence of especially programmed laboratory activities, developed for freshmen, at the Institute of Physics of the University of S˜ao Paulo. It is shown how this activity is employed within a constructive teaching approach, which aims at a growing understanding of the measuring processes and of the fundamentals of correct statistical handling of experimental data