The Malmquist bias is an effect in observational astronomy which leads to the preferential detection of intrinsically bright objects. It was first described in 1922 by Swedish astronomer Gunnar Malmquist (1893–1982), who then greatly elaborated upon this work in 1925. In statistics, this bias is referred to as a selection bias or data censoring. It affects the results in a brightness-limited survey, where stars below a certain apparent brightness cannot be included. Since observed stars and galaxies appear dimmer when farther away, the brightness that is measured will fall off with distance until their brightness falls below the observational threshold. Objects which are more luminous, or intrinsically brighter, can be observed at a greater distance, creating a false trend of increasing in