We develop a general approach to robust inference about a scalar parameter when the data is potentially heterogeneous and correlated in a largely unknown way. The key ingredient is the following result of Bakirov and Sz´ekely (2005) concerning the small sample properties of the standard t-test:...

Many key variables in finance, economics and risk management, including financial returns and foreign exchange rates, exhibit nonlinear dependence, heterogeneity and heavy-tailedness of some usually largely unknown type.The presence of non-linear dependence (usually modelled using GARCH-type...

We propose a new way to construct instruments in a broad class of economic environments: “granular instrumental variables” (GIVs). In the economies we study, a few large firms, industries or countries account for an important share of economic activity. As the idiosyncratic shocks from these...