FNMR rate will increase on age group 0 - 5 as documented by NIST showing the False non-match rate (FNMR) given a False match rate (FMR) of .001 (blue dot) and .0001 (red dot). What this graph shows is that false matches occur more often with younger subjects.
For the visa images, the dots show FNMR by age group for two operating thresholds corresponding to FMR = {0.001, 0.0001} computed over all on the order of 1010 impostor scores. The FMR in each bin will vary also - see subsequent impostor heatmaps in sec. 3.6.2. Given a pair of face images taken at different times, we assign the comparison to the bin that is the arithmetic average of the subject’s ages. This plot shows only the effect of age, not ageing. The number of comparisons in each bin is generally in the thousands, however the first and last bins are computed over 149 and 124 respectively. The error rates in some (adult) cases are zero, and in others the DET is flat so the error rates at the two thresholds are identical. The lines span 1% and 99% of boostrap replicated FNMR estimates.