Here’s why. (a) The Hodrick-Prescott (HP) filter introduces spurious dynamic relations that have no basis in the underlying data-generating process. (b) Filtered values at the end of the sample are very different from those in the middle and are also characterized by spurious dynamics. (c) A statistical formalization of the problem typically produces values for the smoothing parameter vastly at odds with common practice. (d) There is a better alternative. A regression of the variable at date t on the four most recent values as of date t - h achieves all the objectives sought by users of the HP filter with none of its drawbacks.

This paper studies the political influence of individual firms on congressional decisions to suspend tariffs on U.S. imports of intermediate goods. We develop a legislative bargaining model in which firms influence legislators by transmitting information about the value of protection, using verbal messages and lobbying expenditures. Model estimation using firmlevel data on tariff suspension bills and lobbying expenditures reveals that the probability a suspension is granted decreases with each additional firm that expresses opposition. This effect is significantly larger than that of either opponent or proponent lobbying due to the greater information content of verbal opposition and legislative bargaining costs.

Exploiting a discontinuity in childhood Medicaid eligibility based on date of birth, we find that more years of childhood eligibility are associated with fewer hospitalizations in adulthood. For blacks, we find a 7% to 15% decrease in hospitalizations and a suggestive 2% to 5% decrease in emergency department visits, but no similar effect for nonblacks. The effects are pronounced for utilization related to chronic illnesses and for patients living in low-income postal codes. Calculations suggest that lower rates of hospitalizations during one year in adulthood for blacks offset between 2% and 4% of the initial costs of expanding Medicaid for all children.