Microeconometrics researchers have increasingly realized the essential need to account for any within-group dependence in estimating standard errors of regression parameter estimates. The typical preferred solution is to calculate cluster-robust or sandwich standard errors that permit quite...

The health benefits of spas have been hypothesized for centuries. If this hypothesis is correct, spa therapy offers a low cost alternative to more expensive and potentially more invasive medical treatments for ailments such as back pain and arthritis. We use individual-level panel data to...