Top: weights W_s = 1/P_s that correct for bias in detection and survey selection criteria as function of stretch parameter from ∼10⁵ simulations of model Type Ibc lightcurves, while including realistic iPTF cadence and downtime (see Sect. 7.1). Bottom: the impact of the Malmquist bias on the Type Ibc r-band broad fraction estimated from truncated regression fits to the broad and ordinary samples. Changing the redshift limit has a significant impact on the Malmquist bias (see Sect. 7.2).