Outliers and Patterns of Outliers in Contingency Tables with Algebraic Statistics

Abstract. In this paper, we provide a definition of pattern of outliers in contingency tables within a model‐based framework. In particular, we make use of log‐linear models and exact goodness‐of‐fit tests to specify the notions of outlier and pattern of outliers. The language and some techniques from Algebraic Statistics are essential tools to make the definition clear and easily applicable. We also analyse several numerical examples to show how to use our definitions.     

S-I-R Model with Directed Spatial Diffusion

A S-I-R epidemic model is described in which susceptible individuals move away from foci of infection, and all individuals move away from overcrowded regions. It consists of hyperbolic partial differential equations, the sum of these equations being parabolic. Positivity and regularity of solutions are discussed and finite time blow-up of some solutions is illustrated through numerical simulations. A numerical test of the finite time blow-up of solutions is proposed.     

POLITICAL BUSINESS CYCLES IN THE NEW KEYNESIAN MODEL

This paper tests various political business cycle theories in a New Keynesian model with a monetary and fiscal policy mix. All the policy coefficients, the target levels of inflation and the budget deficit, the firms' frequency of price setting, and the standard deviations of the structural shocks are allowed to depend on “political” regimes: a preelection versus postelection regime, a regime that depends on whether the president (or the Fed chairman) is a Democrat or a Republican, and a regime under which the president and the Fed chairman share party affiliation in preelection quarters or not. The results provide evidence that several coefficients are influenced by political variables. The best‐fitting specification, in fact, is one that allows coefficients to vary according to a regime that depends on whether the economy is in the few quarters before a presidential election or not. Monetary policy becomes considerably more inertial before elections and fiscal policy deviations from a simple rule are more common. There is some evidence that policies become more expansionary before elections, but this evidence disappears for monetary policy in the post‐1985 sample. (JEL C11, D72, E32, E52, E58, E63)