Present-day mass functions (colored histograms) and the best-fitting truncated IMFs (solid black histogram) for each population. The completeness limits on the low-mass end appear different for each cluster because of the distance-dependent sensitivity limits. The completeness at the high-mass end is more difficult to evaluate because individual stellar evolutionary histories are governed by the independent ages of the groups. If the mass distribution follows the displayed truncated standard IMF, we estimate the missing mass fraction to be in a range from about 15% for IC 2602 to almost 45% for NGC 2516.