Recently, we've looked at the history of margins, of blowouts, mismatches and upsets, and the history of conversion rates. Today we'll be looking at the history of close games, which I'll define as games that are decided by a goal or less.

Close games have been somewhat rare in VFL/AFL history, with most seasons producing them at a rate no greater than about 15%, and with more recent seasons producing them at even lower rates, as the chart at right depicts. 

The most-recent season, 2015, saw only about 7% of games finish with such a margin, the lowest percentage since 1986 when only about 6.5% of games would have been classified as "close".

Close results though, like periods of good fortune, have not been distributed equally, with teams participating in vastly different proportions of them during different eras. Melbourne, for example, played in no "close" contests at all across the entire 1916-1920 Era, while Carlton's fate was for about 27% of its contests to finish as "close" games across the 1911-1915 Era. That must have made being a fan a slightly harrowing affair, though you would have had the consolation of seeing them win almost two-thirds of these close games. 

(Note that we analyse using eras rather than individual seasons in an effort to reduce some of the small-sample variability evident in teams' season-to-season close game data and that eras are defined as 5-year periods except for the first which we define as running from 1897 to 1905.)

The chart below shows the proportion of close wins and close losses for each team in every era, where draws are counted as half a close win and half a close loss. Each cell is shaded based on the total proportion of close games that a team played in during the era, the overall shading pattern revealing the general decrease in the proportion of such games in more recent times as seen in the chart above.

That said, some teams have still found themselves playing a lot of close games even in the 2011-2015 Era, with Geelong and Essendon both notable examples. For both, about 19% of their games in this era have finished with such a margin, 11% as close wins and 8% as close losses. In contrast though, only about 2% of GWS' games have finished with such a margin in this era, and only about 6% of Gold Coast's.

Looking at the last couple of eras, St Kilda stands out since they've seen 12% of games in the 2011-2015 Era finishing as close games, but only 2% or about 1 in 6 of these finishing as victories. This is in contrast to their 2006-2010 Era experience, which saw them win two-thirds of their close finishes. The Roos are another team to have seen their close game record deteriorate, they having won about 9 in 13 of their close games in the 2006-2010 Era, but only about 2 in 11 of their close games in the 2011-2015 Era.

If we expand our view to take in all of the eras back to 1981-1985 we find that it's Geelong who have, proportionately, been involved in the largest number of close games. Almost 1 in 7 of their games has finished with a margin of 6 points or less and they've emerged successful from these games just over 52% of the time, which ranks them 7th on this statistic.

The team with the best record for winning close games in this period is the Gold Coast, they having won 64% of their 7 close games (4 wins, 1 draw and 2 losses). Next best is Essendon, their 61% win rate based on a larger sample of 105 close games.

The Brisbane Lions have comfortably the worst performance in the 1981-2015 period having won only 30.5 of their 76 close games, which is about a 40% record. St Kilda's 33.5 wins from 82 games (41%) isn't much better.

Gold Coast's 64% record is also the best all-time record of any team, the Brisbane Bears' 59% record coming in second, just ahead of Port Adelaide's. University, at 33%, has the worst all-time record in close games, Adelaide the second-worst at just over 43%.

Proportionately, all-time, Carlton have played in more close games than any other team (about 16%) and Essendon have played in second-most (15%). Amongst the teams that have played more than a handful of games - which excludes GWS and the Gold Coast - the Brisbane Bears have seen their games finish as close games least often (8%), followed by University and Fremantle (both about 10%).

We can also look at each team's Close Win and Close Loss histories separately, which is what's done in the charts that follow (both of which are clickable to access larger versions).

We can see from these charts, for example, the relatively large proportion of Close Wins that Geelong and Port Adelaide have produced in recent eras by comparison with, say, Fremantle and the Brisbane Lions, but also the relatively large proportion of Close Losses that Geelong and Port Adelaide have endured in comparison to these same two teams. This pattern is consistent with the data in the previous table showing Geelong and Port Adelaide as playing a large proportion of close games, and Fremantle and the Brisbane Lions playing smaller proportions. 

Overlaid on both charts are the counts of Premiership and Runners-Up finishes by teams in each era. An analysis of this data suggests a weak link between registering close wins and avoiding close losses on a team's ultimate performance in an era, though moreso for winning Premierships than for finishing as Runners-Up:

• The correlation between the percentage of close wins a team had in an era and the number of Premierships it collected in that era is +0.17
• The correlation between the percentage of close wins a team had in an era and the number of Runner-Up finishes it had in that era is +0.06
• Between them, the 32% of teams registering close wins in 8% or more of their games in an era collected 46% of Premierships and 38% of Runner-Up placings in the matched era.
• The correlation between the percentage of close losses a team had in an era and the number of Premierships it collected in that era is -0.07
• The correlation between the percentage of close losses a team had in an era and the number of Runner-Up finishes in that era is +0.02
• Between them, the 21% of teams registering close losses in 4.5% or fewer of their games in an era collected 28% of Premierships (but only 18% of Runner-Up placings) in the matched era.

That's barely compelling evidence, but so far we've been focussed on aggregate measures while football wisdom asserts that successful teams win more than their share of close games, which might suggest that we should be considering instead a relative measure, which I'll call Nett Close Games and define as the difference between a team's percentage of games finishing as close wins and percentage of games finishing as close losses.

In the first chart, shown below, we colour-code each era for a team on the basis of this nett measure and we show in the cell the components from which the nett figure is derived. The brighter green a cell for a given team and era, the greater the difference between close wins and close losses for that team in that era, while the darker red a cell, the smaller the difference (or the larger the negative difference).

Here we see, for example, that Geelong since the 1961-1965 Era has tended to produce positive Nett Close Game figures, the exceptions being the 1985-1990 and 1991-1995 eras, and that West Coast has produced negative Nett Close Game figures for 4 of the 6 eras of its existence.

We might wonder then, how a team's Nett Close Game performance has related to its ability to win Premierships or finish as Runners-Up. In this next and final version of the chart, we overlay each cell, as earlier, with counts for the relevant team of Premierships and Runner-Up finishes within the era.

Analysing this Nett data in the same way as we did the Close Wins and Close Losses data reveals:

• The correlation between the nett percentage of close wins less close losses for a team in an era and the number of Premierships it collected in that era is +0.19
• The correlation between the nett percentage of close wins less close losses a team had in an era and the number of Runner-Up finishes in that era is +0.03
• 63% of Premierships (and 46% of Runners-Up finishes) in eras have gone to the 46% of teams with positive Nett Close Game values for that same era

That's still only weak evidence for the proposition.

Constraining our attention solely to the eras since 1981 provides even less convincing evidence for recent history, with 46% of Premierships and 46% of Runners-Up finishes in eras going to the 46% of teams with positive Nett Close Game values for that same era.

On balance, I think it's fair to say that the evidence for the proposition that successful teams win more than their share of close games is weak at best. Statistically speaking, if there is an effect, it's a very small one.

It's not true either, by the way, that successful teams avoid playing in close games altogether, since the correlation between the proportion of close games played by a team in an era and the number of Premierships it collected in that era is just +0.07, and between the proportion of close games played by a team in an era and the number of Runner-Up finishes just +0.05.

Here's an alternative hypothesis: close games are largely lotteries and the rate at which generally successful and unsuccessful teams win them will be very similar. As such, they don't provide much information about a team's ability. What will differentiate teams is the rate at which they win games that aren't close. 

To test this, let's use a new metric, the difference between a team's winning rate in close games and its winning rate in non-close games, which are those games decided by at least 7 points. Below is the now-familiar chart for this metric. 

A casual scan suggests that a lot of the green cells, which are for teams winning close games at a higher rate than non-close games, contain no Premierships or Runner-Up finishes, and that the red cells tend to contain many Premierships and Runner-Up finishes. An analysis of the underlying data supports this observation:

• The correlation between teams' winning rate in close games less winning rate in non-close games in an era and the number of Premierships it collected in that era is -0.39
• The correlation between teams' winning rate in close games less winning rate in non-close games in an era and the number of Runner-Up finishes in that era is -0.40
• The 52% of teams that have recorded a negative difference between their winning rate in close games and their winning rate in non-close games for an era have won 83% on Premierships and collected 80% of the Runners-Up medallions in matched eras.

Looking at winning rates in non-close games alone provides the strongest evidence of all, with the correlation between a team's non-close game winning rates in an era and the number of Premierships they collected +0.62, and between this and the number of Runner-Up finishes in the era +0.52.

Our alternative hypothesis seems to be supported by the evidence then. Successful teams don't so much tend to win the close ones, but instead tend to win the ones that aren't close.