The true fraction of repeating fast radio bursts revealed through CHIME source count evolution

Fast Radio Bursts (FRBs) are classified into repeaters and non-repeaters, with only a few per cent of the observed FRB population from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) confirmed as repeaters. However, this figure represents only a lower limit due to the observational biases, and the true fraction of repeaters remains unknown. Correcting for these biases uncovers a notable decline in apparently non-repeating FRB detection rate as the CHIME operational time increases. This finding suggests that a significant portion of apparently non-repeating FRBs could in fact exhibit repetition when observed over more extended periods. A simple population model infers that the true repeater fraction likely exceeds 50 per cent with 99 per cent confidence, a figure substantially larger than the observed face value, even consistent with 100 per cent. This greater prevalence of repeaters had previously gone unnoticed due to their very low repetition rates (similar to 10(-3.5) h(-1) on average). Hence, theoretical FRB models must incorporate these low-rate repeaters. Furthermore, our results indicate a significantly higher repeater volume number density, potentially exceeding observed values by up to 10(4) times, which in turn impacts comparisons with potential FRB progenitors.