Top: best-fit IFMR. Gray shaded region shows 95.4% probability. We parameterize the IFMR as a flexible, continuous piecewise-linear function, leaving both coordinates of the breakpoints free. Because the IFMR flattens at 3.5 ≲ m_in/M_⊙ ≲ 5.5, stars with a wide range of initial masses accumulate at m_WD ∼ 0.8 M_⊙. Points and 1σ error bars show measurements from WDs in wide binaries and star clusters (Catalán et al. 2008a), which are shown for comparison but are not used in deriving our IFMR. Bottom: best-fit IFMR compared to other results from the literature (Weidemann 2000; Kalirai et al. 2008; Williams et al. 2009; Andrews et al. 2015; Choi et al. 2016; Cummings et al. 2016).