The Kentucky Derby (G1) celebrates its 142nd running on May 7 at Churchill Downs, but how is the 20-strong field assembled? Who makes the decision on which horses gets in and which horses are left out of the starting gate on the first Saturday in May?

Once upon a time, for a very long time, graded stakes earnings determined who would take part in the Run for the Roses. In 2012, that all changed when Churchill Downs Inc. (CDI) announced a new points-based system that would be used to qualify three-year-olds for the Kentucky Derby.

The new system includes a number of prep races – from all over the country and even internationally – assigned points based on importance and time of year. It kicks off the year before the Derby in two-year-old contests, but later sophomore preps are where the real points show up.

Winning one of those later events ensures a spot in the Kentucky Derby starting gate, but the risk of losing looms large over the hopefuls as it could mean missing the race entirely.

The entire early prep season is made up of races awarding points on a 10-4-2-1 basis to the respective top four. There were 19 races under that designation heading into the 2016 Kentucky Derby, beginning with the Iroquois (G3) on September 12 at Churchill Downs. The prep season concluded with the Southwest (G3) at Oaklawn Park on February 15.

The latter part of the points system is designated the Championship Series and featured 15 scheduled races for the 2016 Kentucky Derby. Eight of those scheduled races were worth 50-20-10-5 points to the top four, while seven contests served up a guaranteed spot in the Derby gate to the winner with 100-40-20-10 points up for grabs.

The final race in the points system – the Lexington (G3) at Keeneland – is really nothing more than a last-ditch effort for sophomores who are on the verge of making the Derby to earn some points that could tip them over into the coveted top 20. It only offers 10-4-2-1 points to the top four, but the winner’s share could mean the difference between making the field or being forced to stay in the barn.

And what about those graded stakes earnings that previously determined everything? Do they matter at all anymore?

Not really. If two sophomores end up with the same points, then whichever one has more non-restricted stakes earnings is given first preference and placed higher on the Kentucky Derby Leaderboard.

So there you have it, the new, ever-changing (races are added and removed from the schedule every year) way a horse makes it into the Kentucky Derby field.