DNF rate — "how often did they not finish?"

The share of race starts that ended without a classified finish. Formula: races not finished ÷ race starts × 100. Races the driver did not start are excluded from both sides. A disqualification counts as a finish that scored nothing, not a DNF. Why it sits apart from the era-fair rates: unlike a win or a podium, finishing meant something very different in different eras. Cars in the 1950s–70s broke constantly; modern cars almost always reach the flag. A high DNF rate in 1955 says far more about the machinery than the driver. Comparing two drivers within the same season is meaningful — they faced the same conditions. Across eras it's context, not a verdict.

Points-finish rate — "how often did they score?"

The share of race starts that ended in a points-paying position. Formula: races finished in a scoring position ÷ race starts × 100, using that season's real points system. Why it's era-dependent: the number of positions that pay points has changed repeatedly — the top five scored in 1950, the top ten score today. A modern driver has roughly twice as many scoring positions available for the same relative performance, so a higher percentage doesn't necessarily mean a better driver. Like DNF rate, it's shown as context.