Impact of Systematic Sampling on Causality in the presence of Unit Roots

Quite contrary to the stationary case where systematic sampling preserves the direction of Granger causality, this paper shows that systematic sampling of integrated series may induce spurious causality, even if they are used in differenced form.Systematic Sampling, Causality, Unit Roots, Cross covariance

How an Export Boom affects Unemployment

Does trade affect the equilibrium rate of unemployment? To theoretically examine this question, we incorporate firm-union bargaining considerations into a model with a booming external sector and a stagnating manufacturing sector. In the model, a sustained improvement in the terms of trade lowers unemployment. To empirically investigate the predicted determinants of the unemployment rate, we use data for Australia, a country whose prosperity has always depended on the value of its exports. We find strong evidence that higher export prices, capital accumulation in tradeable goods industries and a lower unemployment benefit replacement rate each reduce the equilibrium unemployment rate.

Local helioseismic and spectroscopic analyses of interactions between acoustic waves and a sunspot

Using a high cadence imaging spectropolarimetric observation of a sunspot and its surroundings in magnetically sensitive (FeI 6173 A) and insensitive (FeI 7090 A) upper photospheric absorption lines, we map the instantaneous wave phases and helioseismic travel times as a function of observation height and inclination of magnetic field to the vertical. We confirm the magnetic inclination angle dependent transmission of incident acoustic waves into upward propagating waves, and derive (1) proof that helioseismic travel times receive direction dependent contributions from such waves and hence cause errors in conventional flow inferences, (2) evidences for acoustic wave sources beneath the umbral photosphere, and (3) significant differences in travel times measured from the chosen magnetically sensitive and insensitive spectral lines.Comment: 12 pages, 5 figures, To appear in the Astrophysical Journal Letter