Let’s talk about Jammer Lap Points (further referred to as “JLP”)… I’m a math guy, a stats guy really… it’s in my job title, “Lead Data Analyst”. I’ve analyzed everything from roller derby, esports, corporate travel to education. Roller Derby though, while more driven as a fan-base is largely ignorant of its own stats. So let's look at them!
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| How I feel when people say it won't really change the game... |
- Total Bout time 90 minutes
- Minimum total number of jams
- Theoretical, 0 seconds lead with call, 0 points earned: 180
- Estimated, 0 points to lead, 10 second lap all opposing skaters: 135
- Maximum total number of jams (full 2 minute jams, 30 seconds between): 36
- Looking at 2017 data as a complete year set we have the following bout/score info:
- 5,307 bouts played
- 2,245 of which were in tournament play
- 689 were within 18 points (just guessing that a team gets lead about ½ of the time) or about 13% of the bouts
- 244 in Tournament Play (or approximately 10.8% of the bouts)
- If a team won by less than 18 points (which is adjustable in the viz) I gave the win to the other team so basically flip-flopping every game under 18 points.
- Unfortunately, I don’t have access to the row level data of each games’ scorekeepers or every pass >= 5 I could change to 4 and we could get a DEFINITIVE list of bouts that would have been decided by the JLP change.
First, I wanted to focus on the meta game, commonly referred to in esports as “The Meta.” When we think about most sports, the rules don’t change terribly frequently. Soccer, American Football, Tennis, etc typically are very settled sports, that is to say they don’t have rules that fluctuate very much. Minor changes and typically nothing to do with scoring are changed. Scoring and defensive changes would reasonably cause the largest change to the meta with everything else done in sports in service of either offense (scoring), defense (preventing score), or penalizing bad behavior (personal/team penalties). Let’s get into it!
The chart below shows a scatter plot of all games over the last 3 years with tight games of 18 or less being represented in the red band. You can filter by tournament type or if it was in tournament play at all. Honestly, JLP’s are only affecting about 1 in 10 games. With that said, however, there is a trend in more recent years of it affecting Tournament games more and more… this makes sense as tournaments become better at seeding and finding similarly skilled opponents to play each other.
While it doesn't seem to affect MANY games... think of every "barn burner" of a game you've ever seen. Like... Jacksonville in the tournament this year. Jammer Lap Points MADE A DIFFERENCE in that game. There's no denying that.
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| JLP was a huge part of the comeback against Montreal |
This next viz I built to show individual teams the difference it could potentially make in their record over the years. Put in your own team name at the top, again if you're on mobile you can go to a mobile version by clicking here: https://public.tableau.com/views/RollerDerbyJLPViz/IndividualTeam?:embed=y&:display_count=yes
Ultimately, what I've found is that I lack the access to the row-level stats to truly do correct analysis so this is more of a "close games" analysis but if you know that you're a "5 and done" team typically you can guesstimate how many JLP's your team might average in a bout and put those numbers in to see for yourself!
I think the argument that a person or the public not understanding the rules of a game means that you're catering the game to the enjoyment of the fans and the skillfulness of the athletes/refs. I know that this rules change is going to happen but it's worth noting that now things; like the highest point jam record will never be touched, a 20 point jam suddenly becomes a big deal, and previously a 40 point differential was the tipping point to statistically winning a bout... now that will fall to around 32 points.
With all that said, there are plenty of stats nerds in derby that would run these numbers and I think there should be open debate about rules changes that affect the meta game so seriously.
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| How I feel about the audience not getting the JLP rules... |
Addendum: Some people (Thanks Skate Beckett!) pointed me towards WFTDA's stats page to get more accurate data... it took a TON of cleaning (hence why this is being published much later than I initially intended.) With that said, I did the following in the same format... but the WFTDA stats data is super limited only having up to beginning of 2018 and primarily only having tournament info included. I actually reformatted the data at the jam level and reduced anything over 5 points in a pass to 4 points. Ultimately what that led to was the following viz: https://public.tableau.com/views/RollerDerbyJLPViz/WFTDAMeta?:embed=y&:display_count=yes
Also what this resulted in was a closer average game point differential going from a point difference of 63.1 to 53.8. So even though I feel deep in my soul that this is one of those things we should fight, it ultimately should lead to some closer bouts in the long run! So yay!?
