Who wins a NBA game when it goes into overtime?
Which team is more likely to win when a NBA game goes into overtime? The home team? The favourites? The underdogs? As the NBA season is in full swing, today on the blog Andrew takes a look at the question.
Over the last 10 NBA seasons, roughly 6% of games have extended to overtime. Today on the blog I take a look at what happens when a NBA game does head into the extra period. Who is more likely to win? Do home clubs excel in overtime? Do underdogs fall away when going into extended minutes? I will try to answer each of these questions and more.
Home vs Away
Firstly let's do a simple home v away breakdown. Over the last 10 NBA seasons, home clubs won just under 52% of all overtime games. When the game went into a single overtime period, home clubs were consistent, winning just under 52% of games.
When the game went into double overtime, road clubs won 51% of the time, although the sample size was just 100 games played.
Lastly, though an even smaller sample size, home clubs were far superior when a game went into triple overtime, winning just under 71% of the time.
Home favourites vs Away favourites
But let's get into some betting analysis. The chart below shows the overtime winning percentages for both home favourites and away favourites over the last 10 NBA seasons.
As we can see, when the home club starts the game as favourites, they win in overtime just over 56% of the time. This was over a sample size in excess of 500 games.
You might have thought that home underdogs would do better, but over the last 10 NBA seasons, away favourites have beaten home dogs in overtime just over 57% of the time, across a sample size of over 200 games.
Favourites big & small
Ok, now let's dig a little bit deeper. The chart below shows the overtime winning percentages of both home favourites and away favourites grouped by rank of favouritism.
We can see that when home clubs started the game as a favourite of at least 9 points, when the game went to overtime, they won just over 72% of the time. When home clubs started favourites between 6 and 8.5 points, they won in overtime just over 61% of the time.
The most interesting observation is that when the game's starting betting line was between home clubs as favourites of at most 5.5 points all the way down to the away club being favourites of at most 2.5 points, the match was pretty much a 50-50 proposition when heading into extra time. In these situations, the home clubs won in overtime just over 49% of the time the last 10 NBA seasons. And importantly, these games consituted roughly 50% of all overtime games played over that span.
Finally, when away clubs started favourites of at least 3 points up to favourites of 6 points, they won in overtime just under 57% of the time, while when away clubs were favourites of at least 6.5 points, they won in overtime over 77% of the time.
So what did we learn?
Well for one thing we learned that while home favourites of 6 points or more and away favourites of 3 points or more win at a reasonably expected rate, there is a sweet spot inbetween where overtime games are a bit of a coin toss.
We also can see that away favourites tend to do a little bit better than home favourites. For example, home club favourites of at least 6.5 points won in overtime just under 66% of the time, while away favourites of the same kind won in overtime over 77% of the time.