@unpublished{publication-23235,
	author={Winkelmann, Rainer},
	institution={University of Zurich},
	issn={1664-7041},
	number=426,
	pages=20,
	series={Working paper series / Department of Economics},
	title={Neglected heterogeneity, Simpson’s paradox, and the anatomy of least squares},
	year=2023,
}