Monday, 3 November 2014

Premier League conversion rates drive media storylines

I was going through my rolling 5 week conversion rates this morning & it was fascinating to see just how many of the general season storylines can be defined with reference to these numbers.  It being week 10 now, I can split the start of the season into two halves & show where teams were after 5 and 10 games.  We're on a similar path to PDO here but it's informative to split the two sides of for & against conversion.  In this case I'm going to use just goals to all shots. By season's end we would largely expect the better teams to have a rate somewhere between 0.11 & 0.17 'for' and dominance over the 'against' numbers.  A bad team can expect something like 0.06-0.09 'for' and a higher figure against.  This is not definitive but a good general guide.


5G Conv Rate F A
1st 5 0.13 0.14
2nd 5 0.08 0.16

Mixed results throughout considering their general dominance in games.
Why? Their opposition are converting at a higher rate than they are, dramatically so in recent games.  This can be the difference between a draw and a win as the Hull game amply demonstrated.

Aston Villa:

5G Conv Rate F A
1st 5 0.11 0.07
2nd 5 0.02 0.14

A good start followed by no goals & no points.
Why? To start, their average conversion rate dominated the opposition's sub-par conversion rate. Latterly, not only have they stopped scoring but the opposition conversion rate has doubled.  Result? No wins, not even any draws.


5G Conv Rate F A
1st 5 0.02 0.07
2nd 5 0.07 0.14

It's bad, and it's still bad.
Why? In this league, they are bad.


5G Conv Rate F A
1st 5 0.19 0.12
2nd 5 0.16 0.06

League domination followed by league domination.
Why? These are extremely high rates 'for' and are likely to regress over time.  Regardless, until this point Chelsea have a significant advantage in their shooting efficiency over their opponents


5G Conv Rate F A
1st 5 0.17 0.22
2nd 5 0.12 0.06

A poor start & a recent upturn in results.
Why? Terrible early opposition conversion numbers couldn't overcome their own high number.  More recently, they are converting at twice the rate of their opponents and lo and behold are getting better results.


5G Conv Rate F A
1st 5 0.14 0.08
2nd 5 0.14 0.08

Listen to Steve Bruce & you get the feeling he's pinching himself each week.
Why? Because he's riding a consistently positive +/- conversion rate & eventually, backed up by poor shot totals, they are likely to get found out.


5G Conv Rate F A
1st 5 0.18 0.08
2nd 5 0.04 0.13

Leicester had a great start & looked well set, recent form hasn't been so good.
Why? Scoring 5 against Utd helped their early numbers but we can see they were well in credit early on.  Since the Utd game, it has been Burnley rate bad.


5G Conv Rate F A
1st 5 0.10 0.17
2nd 5 0.07 0.09

It's been a struggle.
Why? No dominance here. The opposition number has come down but has been followed by the 'for' totals.  Liverpool haven't managed to get ahead of the count yet, most notably poor Mario.  This will probably change soon; they aren't suddenly a bad team.

Man City:

5G Conv Rate F A
1st 5 0.12 0.10
2nd 5 0.12 0.09

'They aren't firing yet' and such and such.
Why? Well, they're doing just fine.  All criticism is measured against last season's stream of thrashings dealt out which were powered in part by great conversion numbers.  This year is less flashy, as witnessed in the 1-0 derby win.

Man Utd:

5G Conv Rate F A
1st 5 0.14 0.16
2nd 5 0.10 0.11

Mixed results for Van Gaal, a tough start.
Why? Like Liverpool, there is no dominance here & no dominance can equal hard times.


5G Conv Rate F A
1st 5 0.07 0.20
2nd 5 0.09 0.08

'Newcastle were rubbish but they're getting their act together now.'
Why? They were never that bad, it was just their opposition conversion numbers were super high & they were converting nothing.  Things have settled down now & over the last 5, they're edging it.


5G Conv Rate F A
1st 5 0.16 0.13
2nd 4 0.15 0.11

Nobody is talking about Palace.
Why? Maybe the first thing Warnock said was 'What did Pulis tell you? Do that.'   As it stands they're ahead of the game, most probably at an unsustainable level & these great numbers haven't powered that many points. They aren't safe by any means.

edit: some quick regression vs Sunderland, they now stand at 0.12/0.15 for the 2nd 5, no longer ahead of the game?


5G Conv Rate F A
1st 5 0.04 0.15
2nd 5 0.11 0.12

'QPR are so bad, almost laughably so'
Why? Well, they were, at least away from home & throw in 4% conversion early on and hey presto, storyline.  More recently they've shown more 'fight'... also known as improved conversion numbers.


5G Conv Rate F A
1st 5 0.15 0.08
2nd 5 0.16 0.04

This season's surprise package.
Why? All their underlying numbers are good but, and this is a big but, they aren't going to sustain a 4:1 ratio shot conversion like the last 5 games.  That is a silly number and backs up a 2:1 ratio from the first 5.  They have tougher games ahead, most notably in December & there is no way both these numbers don't regress, the question for their long term prospects being, how much?


5G Conv Rate F A
1st 5 0.09 0.09
2nd 4 0.05 0.16

Lots of draws, lots of 'pluckiness' followed by a trouncing.
Why? Early parity is reflected here, and being slaughtered by Southampton skews the latter 'against' number.  Nevertheless, they aren't converting chances & that needs to change.

edit: so an impressively efficient 3/8 goals to shots v Palace? Palace scored their only SoT?
They're now at 0.11/0.19 for the 2nd 5, which at least sorts out the 'For' section.


5G Conv Rate F A
1st 5 0.06 0.08
2nd 5 0.09 0.10

It's Stoke; not a lot going on.
Why? They struggle to score but are solid in defense.  Nobody converts at a high rate in Stoke matches.  Once more the ghost of Pulis looms.


5G Conv Rate F A
1st 5 0.17 0.07
2nd 5 0.11 0.06

Fast start, slowing recently.
Why? They've spent the year taking their chances & their opposition hasn't.  The fast start was very fast due to a very high 'for' number but the 0-0 at Everton whilst creating little & being slightly fortunate not to concede is a clear indication of what's going on now.


5G Conv Rate F A
1st 5 0.12 0.10
2nd 5 0.09 0.13

All very average.
Why? Two sets of 7 points in 5 games, with the latter 'against' figure skewed by the Man City game, as with all their other underlying numbers, Tottenham need to improve all over to hope to climb the table.

West Brom:

5G Conv Rate F A
1st 5 0.05 0.14
2nd 5 0.16 0.08

No wins in the first 4 then a better set of results.
Why? Initially they couldn't score but since getting going, their conversion has taken off, despite worsening opposition shot numbers that have intriguingly inversely followed the conversion rate, which is unique in this study. 

West Ham:

5G Conv Rate F A
1st 5 0.13 0.14
2nd 5 0.15 0.08

'They're flying! Big Sam is God!'
Why? Headline making wins against Liverpool and City have cemented the storyline but recent results and the surge up the table have been largely powered by a lovely 2:1 conversion ratio.  People have short memories: West Ham were fine but unremarkable until they beat Liverpool, but now expectation is high.  Most likely the 2-2 at Stoke is a more accurate reflection of their ability and expectation this year.


As I think i've shown, the conversion rate has had a pretty strong impact on creating the storyline for most clubs in the league.  The teams most obviously doing well here are likely to find their dominance reducing over time, with the majority of the better teams retaining or achieving long term dominance and the lesser teams fading away or remaining inefficient.  The truth here is that these rates aren't predictive in themselves but do inform the storylines the media seize upon, alongside the obvious hooks such as actual results, league position or an eye-catching win or two.

Systems can affect the efficiency as well as obvious team power; we might expect a Mourinho team to be effective at minimising the opposition but could not predict that Diego Costa would convert so freely and obvious outliers can be expected to fall back within expected norms in time.

Last season Liverpool and Man City both converted around the 15-16% mark & exerted a +0.05 dominance overall.  In contrast, Norwich converted at 0.06 over the whole season which was significantly lower than any other team.  The three relegated teams ran at -0.03, -0.03 & -0.05, not intrinsically season defining but along with other inefficent teams, amongst the season lows.  As a loose view of shooting efficiency, these numbers are an interesting guide.

Thanks for reading!

(PS: I've not factored in own goals for this, you could and they would have an impact, but the general emphasis would remain.)

Have you read this week's round up? Check it out here . It's got chat about Liverpool and Tottenham's strange weekend formations, a criticism of quarterback Rooney & more.
The column runs every week, so come back again!

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