Veil of Darkness: Live sample

This compares stops just before and just after sunset, holding clock time and location fixed. After dark, a driver’s race is less visible. If the share of stops of Black drivers falls after dark, that signals bias tied to visibility.

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    Before dark
    After dark

    Method in one minute

    • Compare stop shares in a narrow window around sunset.
    • Hold fixed area and clock time to reduce traffic-pattern confounds.
    • Key signal is the change in the share of stops of Black drivers.
    • Drop after dark points to bias tied to visibility, not driving mix.

    This is a visibility instrument, not a full model of policing. It tests whether visibility alone moves stop patterns.

    Sources: Stanford Open Policing Project (openpolicing.stanford.edu); Pierson et al., Nature Human Behaviour (2020).