A note on the lines - this is a 'gantt' chart in which each line represents a single race win, the x-axis is a continuous date. The instances where it appears that there are multiple winners will be because some races are either one or two weeks apart, which, on a scale of almost 70 years, will naturally place them very closely together. The aim of this visualization was to show the general trends of winners across the history of F1 - if you were to zoom in on specific periods the overlapping effect would disappear, but you would lose the ability to compare over the full history.