Cumulative histograms of the discovery years of several different subclasses of UCB, highlighting the impact of different surveys on the make-up of the known sample. SDSS led to an increase in the discoveries of low-state systems (which should dominate in a volume-limited sample), while PTF and ASAS-SN led to rapid discoveries of outbursting systems detected photometrically. ZTF has led to a sharp rise in the number of eclipsing systems.