Is the political business cycle for real?

This paper's macroeconomic model combines features from both real and political business cycle models. It augments a standard real business cycle tax model by allowing for varying levels of government partisanship and competence in order to replicate two important empirical regularities: First, that on average the economy expands early under Democratic presidents and contracts early under Republican presidents. Second, that presidents whose parties successfully retain the presidency have stronger-than-average growth in the second half of their terms. The model generates both of these features in conformity with U.S. post-World War II data.Business cycles

Optimal phosphorus loading for a potentially eutrophic lake

dynamic programming;sustainable development;ecology

Is the Political Business Cycle for Real?

This paper constructs and examines a macroeconomic model which combines features from both real and political business cycle models. We augment a standard real business cycle tax model by allowing for varying levels of government partisanship and competence in order to replicate two important empirical regularities: First, that on average the economy expands early under Democratic Presidents and contracts early under Republican Presidents. Second, that Presidents whose parties successfully retain the presidency have stronger than average growth in the second half of their terms. The model generates both of these features that conform to U.S. Post World War II data.Political business cycle

A Dynamic Structural Model for Stock Return Volatility and Trading Volume

This paper seeks to develop a structural model that lets data on asset returns and trading volume speak to whether volatility autocorrelation comes from the fundamental that the trading process is pricing or, is caused by the trading process itself. Returns and volume data argue, in the context of our model, that persistent volatility is caused by traders experimenting with different beliefs based upon past profit experience and their estimates of future profit experience. A major theme of our paper is to introduce adaptive agents in the spirit of Sargent (1993) but have them adapt their strategies on a time scale that is slower than the time scale on which the trading process takes place. This will lead to positive autocorrelation in volatility and volume on the time scale of the trading process which generates returns and volume data. Positive autocorrelation of volatility and volume is caused by persistence of strategy patterns that are associated with high volatility and high volume. Thee following features seen in the data: (i) The autocorrelation function of a measure of volatility such as squared returns or absolute value of returns is positive with a slowly decaying tail. (ii) The autocorrelation function of a measure of trading activity such as volume or turnover is positive with a slowly decaying tail. (iii) The cross correlation function of a measure of volatility such as squared returns is about zero for squared returns with past and future volumes and is positive for squared returns with current volumes. (iv) Abrupt changes in prices and returns occur which are hard to attach to 'news.' The last feature is obtained by a version of the model where the Law of Large Numbers fails in the large economy limit.

Opsin expression predicts male nuptial color in threespine stickleback.

Theoretical models of sexual selection suggest that male courtship signals can evolve through the build-up of genetic correlations between the male signal and female preference. When preference is mediated via increased sensitivity of the signal characteristics, correlations between male signal and perception/sensitivity are expected. When signal expression is limited to males, we would expect to find signal-sensitivity correlations in males. Here, we document such a correlation within a breeding population of threespine stickleback mediated by differences in opsin expression. Males with redder nuptial coloration express more long-wavelength-sensitive (LWS) opsin, making them more sensitive to orange and red. This correlation is not an artifact of shared tuning to the optical microhabitat. Such correlations are an essential feature of many models of sexual selection, and our results highlight the potential importance of opsin expression variation as a substrate for signal-preference evolution. Finally, these results suggest a potential sensory mechanism that could drive negative frequency-dependent selection via male-male competition and thus maintain variation in male nuptial color

Oak Savanna Restoration: A Case Study

A degraded oak savanna in southwestern Wisconsin is being restored using intensive cutting of undesirable shrubs- buckthorn (Rhamnus cathartica), prickly ash (Zanthoxylum americanum), honeysuckle (Lonicera spp.)-and selective removal of trees that are crowding the open-grown bur (Quercus macrocarpa) and white (Q. alba) oaks. Land use records and historic aerial photographs have been used to guide the restoration process. Slippery elm (Ulmus rubra), black walnut (Juglans nigra), black cherry (Prunus serotina), and black oak (Q. velutina) are being removed by cutting and burning or by converting to lumber or firewood. Hundreds of aspen (Populus tremuloides and P. grandentata) have been killed by girdling with subsequent cutting and burning. Management involves controlled burns and extensive weed control. Removal of invasive shrubs and trees has exposed the ground layer to higher light intensities and stimulated the growth of savanna forbs and grasses. A number of typical herbaceous savanna species have reappeared after clearing or have been successfully introduced from local sources. However, control of brambles (Rubus spp.) and regrowth of buckthorn and honeysuckle remain principal problems. One savanna species endangered in Wisconsin-purple milkweed (Asclepias purpurascens)-was first seen in the savanna after a single controlled burn, and appears to be spreading. The redheaded woodpecker (Melanerpes erythrocephalus), a typical savanna bird, was first seen after shrub and canopy clearing in the savanna. Tree removal is a slow and expensive operation, and strategies for preventing damage to the groundlayer during tree removal had to be devised. About 70 acres (28 hectares) of savanna have been restored during nine years