For most of the season, unlike much of the rest of the football league, the points accrued by teams has had a far stronger correlation to its PDO score than its efficiency at producing shots at the opponents goal.
However, we are starting to see that trend correct quite strongly now, although it has not reversed itself just yet.
|Position||Team||Played||Won||Drawn||Lost||Goals For||Goals Against||Goal Difference||Points|
As we can see from the two graphs further below, team shots on target share now has a correlation (r2) value of 0.5363 with points won, compared to an r2 value of 0.6699 for PDO (a rather catch-all statistic for "luck") and points.
Just a few weeks ago the shots of target correlation was much lower than this.
|Position||Team||Shots for total||Shots against total||Corsi/TSR||shots on target for total||shots on target against total||Shots on target share||Shooting % For||Save %||PDO|
These graphs serve two purposes: first to give an overall idea of the spread of the points gained by teams throughout the league, and second, by labeling the data points we can see which teams have over- or under-achieved on points obtained compared to their performances - a potentially important method of deducing how teams are likely to perform throughout the rest of the season.
Let's start with the shots on target (SoT) vs points graph.
We can see the line of best fit dividing the points fairly evenly - some teams actually sit directly on the line, but most are varying distances away. One way we can look at this graph is to gauge the difference from where clubs should be on the linear relationship, and where they actually are. These distances are important - the further away from the line of best fit, the greater the under- or over-achievement.
In this instance, teams above the line have collected a smaller points total than their share of the shots on target warrants (more shots on target, but fewer points). At the top end of the table, we can see Bournemouth, Middlesbrough and Norwich should actually be even better than they off already, while further down the table Brighton (who I've raised many times previously) stand out as deserving of more points.
In contrast, those below the line have out-performed their shots on target share and collected more points than they deserve. Ipswich, Derby, Brentford and Wolves stand out here, while lower down the table Charlton, Birmingham, Bolton and (most worryingly, perhaps) Leeds have taken more points than they could have been expected to claim following this trend.
If we look at the PDO vs points graph we can see the teams in general more closely grouped around the line of best fit - hence the stronger r2 correlation value.
If we want to interpret this graph the same way we have the previous one, we need to assume that PDO is a linear predictor of points. While this may appear to be true at the moment, it's widely held (though not by all) that PDO is give-or-take entirely random, hence the frequent references to it being a signifier for "luck" or variance within performance.
However, in this instance, if we want to suggest that PDO does have a linear relationship (at least temporarily) then for interpreting the graph it highlights those teams that have benefited most from PDO so far this season (above the line) or suffered from it (below the line).
And again the bigger the distance, the greater the effect.
So, for example, Bournemouth has actually collected 48 points, which they should have "needed" a PDO of around 110 to do so. Meanwhile, third placed Derby's PDO is so high that the Rams should have collected around another 10 points.
As I say, much of this discussion can be considered irrelevant (if you believe PDO to be essentially random) - but it acts as a nice indicator to show those teams perhaps more blessed by good PDO during the season so far.
Interestingly, again, Leeds are quite well above the line. If both these trends correct then it could be an even messier second half of the season for the Yorkshire club.
Much of this backs up the shots on target vs PDO graph higher up the page, but I feel it helps to show some of these trends in a different way sometimes.
Finally, Norwich.I deliberately mentioned earlier on that Norwich were one of those most under-served in the shots on target vs points comparison. The Canaries sacked/pushed overboard/accepted the resignation of Neil Adams this week, something I believe was probably more over-reactionary to a rough one month spell of PDO and a cup upset at Preston.
I'll have a separate post soon going in to more detail on Norwich's performance this season, but suffice to say, sometimes shit happens and its how you react to it that counts.
I don't think the Norwich board have reacted well at all.