Blocks and Assists, Home and Away

[Mike G]

At this time, NBA teams have averaged 20% more blocked shots at home. There's an enormous spread in the distribution:

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tm    h/aBk      tm   h/aBk
NOP   3.37      Den   1.14
Sac   2.96      Por   1.13
Phx   2.03      Mem   1.10
Cle   1.63      Min   1.09
SAS   1.53      Okl   1.04
Phl   1.49      Was   1.03
Mia   1.42      LAC   1.00
Det   1.36      Bos    .98
Chi   1.35      GSW    .95
Uta   1.35      Dal    .95
Hou   1.31      Cha    .91
Orl   1.21      Tor    .81
Ind   1.21      Mil    .75
Atl   1.18      Brk    .73
LAL   1.18      NYK    .66

The Pelicans' Anthony Davis is averaging 6 blocks at home, vs 1.6 on the road. Their #2, Jason Smith, has 11 of 14 at home.
The Kings have played just 3 road games. DeMarcus Cousins has blocked one shot away from home and 14 in Sacramento.
The Suns' Miles Plumlee has gotten 3.0 bpg in Phoenix and 0.8 elsewhere.

Assists are being granted at home -- as a fraction of FG -- just 4.3% more frequently than on the road.

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tm   h/aAs      tm   h/aAs
NOH   1.26      Tor   1.04
Dal   1.23      Bos   1.04
Cle   1.18      Cha   1.03
LAL   1.17      Orl   1.02
Mil   1.16      Por   1.01
Phl   1.14      Hou    .99
SAS   1.13      Det    .99
GSW   1.13      Mem    .98
Okl   1.12      Was    .98
Den   1.10      Ind    .96
Sac   1.06      Mia    .95
Min   1.05      NJN    .94
Chi   1.05      Uta    .88
Atl   1.05      Phx    .82
LAC   1.04      NYK    .80

Well, the Pelicans also head the list here.
Jrue Holiday is getting 8.5 apg at home vs 5.2 on the road. NOP avg 40 FG at home vs 37 away.
Monta Ellis averages 7.3 Ast in Dallas and 4.0 elsewhere. Mavs getting 1.8 more FG at home.

Knicks at the bottom of both lists. But they have been better on the road.

League leaders in Blocks and Assists per game, along with their Away averages:

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Blk    player    tm   aBlk       Ast    player    tm   aAst
4.4   Hibbert   Ind    3.8      12.5   Paul      LAC   11.2
4.0   Davis     NOP    1.6       9.7   Wall      Was    8.4
2.8   Lopez     Brk    3.6       8.8   Rubio     Min    8.8
2.2   Howard    Hou    2.2       8.7   Curry     GSW    8.2
2.1   Ibaka     Okl    2.0       8.7   Teague    Atl    7.7
2.1   Jordan    LAC    2.2       8.6   Lawson    Den    9.4
2.1   Horford   Atl    1.6
2.0   Plumlee   Phx    0.8

[Bobbofitos]

So the Pelican scorekeepers are really massaging the stats eh

[Mike G]

Maybe. This just establishes a base point for future reference.
But the team is +8.2 ppg at home vs -10.4 on the road -- a cool 18.6 ppg difference.
A. Davis is shooting .101 better FG% at home.

Assists are very subjective, blocks less so. The most universal home court statistical advantage may be foul (and FT) disparity. What was a foul on the road may be a 'clean block' at home. So that would be on the refs; and give some credit to enthusiastic fans, for influencing the refs.

[Mike G]

Anthony Davis sits for a few weeks as the league leader in Blk/G
In 8 home games, he has gotten 5.25 per game.
In 8 away games, he averages 2.0

Interestingly, his foul rate is also higher at home.
He's an .846 FT shooter (almost 90% on the road).
His alleged Blk% is 9.2 -- among the top 15 since 1978.
Nobody has had a Blk% of 8.0 or greater and shot .800+ on FT. Shawn Bradley came closest.

[Mike G]

Note: Previous posts are from last season.

Top 10 shotblockers this young season, home and away splits.

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shot blockers         Minutes      Blocks     Blk/36            
2014-15    tm   G    home away   home away   home away   Blk/G  xhBlk  adj/G
A Davis   NOP   23   331   473    35   28    3.8   2.1    2.74   15.4   2.07
D Jordan  LAC   25   453   383    40   21    3.2   2.0    2.44   15.2   1.83
Ibaka     Okl   25   369   428    28   30    2.7   2.5    2.32    2.1   2.23
Duncan    SAS   22   311   384    24   26    2.8   2.4    2.27    2.9   2.14
Drummond  Det   26   411   376    24   21    2.1   2.0    1.73    1.0   1.69

Gobert    Uta   26   228   235    25   20    3.9   3.1    1.73    5.6   1.52
Hibbert   Ind   22   288   305    20   24    2.5   2.8    2.00   -2.7   2.12
Bogut     GSW   20   224   279    16   28    2.6   3.6    2.20   -6.5   2.52
Smoove    Det   26   447   397    19   28    1.5   2.5    1.81  -12.5   2.29
B Wright  Dal   27   237   268    16   26    2.4   3.5    1.56   -7.0   1.81

My bet on "best" shot blockers would be in the away Blk/36 column
xhBlk column is 'extra (or excess) blocks given at home, relative to away rates'.
Final column is 'adjusted' Blk/G based on away Blk/36

A better estimate would involve looking up opponent FGA in home and away games, but I'm too lazy to do that.
Around the league, players are getting 16% more blocks at home.
Thus far, assists are only about 1.7% more numerous at home, as a percentage of FG made.

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assists             Minutes      Assists      Ast/36            
2014-15  tm   G   home  away   home  away  home  away   Ast/G  xhAst  adj/G
Rondo   Bos   22   458   242    157   80   12.3  11.9   10.77   5.6   10.52
Wall    Was   24   547   315    172   82   11.3   9.4   10.58  29.6    9.35
Lawson  Den   24   396   502    117  137   10.6   9.8   10.58   8.9   10.21
Paul    LAC   25   448   415    127  115   10.2  10.0    9.68   2.9    9.57
Lowry   Tor   26   530   369    120   83    8.2   8.1    7.81    .8    7.78

Of these 5, 4 have very small dropoffs, as might be expected when your team doesn't shoot as well.
The Wizards have gotten 3.3 more FG/G at home, and John Wall assists on about 1/4 of them. So that may be ~half of his H/A disparity.

[fpliii]

Mike G - Bit of an old bump, but I saw you discussing the topic in another thread, and didn't want to derail the topic.

Have you done similar research on rebounds/steals/turnovers/fouls? If so, do you think there is a legitimate bias (if yes, how does it compare to blocks/assists bias)?

[ampersand5]

I made this for something else and was going to post here later.

teams definitely have the ability to inflate/deflate stats. question is - what is a better strategy, inflating or deflating?

[Mike G]

Have you done similar research on rebounds/steals/turnovers/fouls? If so, do you think there is a legitimate bias (if yes, how does it compare to blocks/assists bias)?

There is a 'true' homecourt advantage which affects the final score. Crediting an assist or a block, as adjunct to a made or missed FG, does not relate to point differential.

Fouls are definitely correlated (inversely) to blocks and also to MOV. Surely they also correlate (home vs away) to Reb, Stl, TO. Do players really play better at home? Or are refs favoring the home team? Either way, it's not the arbitrary scorekeeper bias, except that they may register 'make-up blocks' when they think the ref called it a foul earlier.

Besides home bias, scorekeepers vary in their generosity toward visiting teams. Unless NBA teams play differently against various opponents, there shouldn't be a lot of variation in aggregate opponent rates. Scorekeepers who are benevolent toward the home team also tend to be generous toward their guests; but not always.

A team's Away rate (Ast/FG and Blk/OpFGA) not only averages the generosities of all the league's (other 29) scorekeepers, it also neutralizes the home favoritism. When assist and block rates are notably inflated, it not only overrates certain players (at the expense of others); perhaps more seriously, it throws a curve ball at our attempts to find good correlations between these rates and players' values.

[Mike G]

In career playoff games, you can get home games only, and away games only -- from 1985 thru 2014 :
http://bkref.com/tiny/dkTmM
From the top 100 in assists, in home games and away games, 90 players make both lists.
Of those 90, the avg ratio of (Away Ast/36Min)/(Home Ast/36Min) = .904 : In playoff games, assists have been granted 10.7% more liberally at home. That ratio is shown as a/h
Part of this is due to more team FG at home, I'm guessing. But I'm not correcting for that, at this point.

Extra Home Assists = (HomeAst)*(1-a/h)

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xHAst   Playoffs    hAs36 aAs36  a/h      a/h    Playoffs      hAs36 aAs36 xHA
147  Jason Kidd      8.4   6.6   .79      .73  Richard Hamilton 3.8   2.8   74
141  Tony Parker     6.0   4.6   .77      .74   John Paxson     4.8   3.6   46
130  Magic Johnson  12.8  11.0   .86      .75   Byron Scott     2.9   2.2   56
99   Kevin Johnson   9.6   7.8   .81      .76   Charles Oakley  2.3   1.7   38
93  Chauncey Billups 6.2   5.0   .80      .76   John Starks     5.3   4.0   53
86   Mark Jackson    9.4   7.8   .83      .77   Tony Parker     6.0   4.6  141
74   Rajon Rondo     9.3   7.8   .85      .77   Michael Cooper  6.3   4.9   60
74  Richard Hamilton 3.8   2.8   .73      .78 Anfernee Hardaway 6.0   4.7   49
63   Larry Bird      6.4   5.4   .84      .79   Jason Kidd      8.4   6.6  147
60   Michael Cooper  6.3   4.9   .77      .79   Brian Shaw      6.2   4.9   46
59   Kobe Bryant     4.6   4.1   .89      .79   Vinnie Johnson  4.6   3.7   35
56   Byron Scott     2.9   2.2   .75      .79   Pau Gasol       3.6   2.8   43
56  Shaquille O'Neal 2.8   2.3   .83      .80  Chauncey Billups 6.2   5.0   93
55   Clyde Drexler   6.1   5.4   .89      .81   Kevin Johnson   9.6   7.8   99
53   John Starks     5.3   4.0   .76      .82   Horace Grant    2.3   1.9   36
52   John Stockton  10.6  10.1   .95      .83   Mark Jackson    9.4   7.8   86
49 Anfernee Hardaway 6.0   4.7   .78      .83   Patrick Ewing   2.1   1.7   25
46   John Paxson     4.8   3.6   .74      .83   Kevin Durant    3.6   2.9   27
46   Brian Shaw      6.2   4.9   .79      .83   Doc Rivers      8.0   6.7   44
44   Doc Rivers      8.0   6.7   .83      .83  Shaquille O'Neal 2.8   2.3   56
43   Pau Gasol       3.6   2.8   .79      .84   Rasheed Wallace 1.8   1.5   23
40   Deron Williams  8.6   7.4   .86      .84   David Robinson  2.6   2.2   24
40   Steve Nash      9.3   8.6   .93      .84   Larry Bird      6.4   5.4   63
39   Jeff Hornacek   4.2   3.7   .86      .84 Russell Westbrook 6.9   5.8   38
39   Chris Paul      9.6   8.3   .87      .85   Rajon Rondo     9.3   7.8   74
38 Russell Westbrook 6.9   5.8   .84      .85   Toni Kukoc      4.6   3.9   28
38   Charles Oakley  2.3   1.7   .76      .85   Chris Childs    6.3   5.4   26
36   Sam Cassell     6.4   5.7   .88      .85   Paul Pressey    7.7   6.6   32
36   Horace Grant    2.3   1.9   .82      .86   Deron Williams  8.6   7.4   40
36   Avery Johnson   7.7   6.8   .88      .86   Magic Johnson  12.8  11.0  130
35   Vinnie Johnson  4.6   3.7   .79      .86   Jeff Hornacek   4.2   3.7   39
34   LeBron James    5.6   5.3   .94      .87   Chris Paul      9.6   8.3   39
32   James Worthy    3.4   2.9   .87      .87   James Worthy    3.4   2.9   32
32   Paul Pressey    7.7   6.6   .85      .87   Mike Bibby      4.6   4.0   29
30   Derek Fisher    3.3   3.0   .90      .87   Mookie Blaylock 6.4   5.6   24
30   Gary Payton     5.5   5.1   .93      .87   Allen Iverson   5.1   4.5   29
30   Dennis Johnson  7.0   6.4   .92      .88   Chris Webber    3.9   3.4   18
30   Scottie Pippen  4.8   4.5   .95      .88   Mark Price      7.5   6.6   20
29   Manu Ginobili   5.0   4.6   .92      .88   Boris Diaw      4.6   4.1   21
29   Mike Bibby      4.6   4.0   .87      .88   Avery Johnson   7.7   6.8   36
29   Allen Iverson   5.1   4.5   .87      .88   Sam Cassell     6.4   5.7   36
28   Toni Kukoc      4.6   3.9   .85      .89   Clyde Drexler   6.1   5.4   55
27   Kevin Durant    3.6   2.9   .83      .89   Rod Strickland  9.4   8.3   21
26   Tim Duncan      3.0   2.8   .93      .89   Joe Johnson     3.3   3.0   17
26   Chris Childs    6.3   5.4   .85      .89   Kobe Bryant     4.6   4.1   59
25   Patrick Ewing   2.1   1.7   .83      .89   Nick Van Exel   5.4   4.9   19
24   David Robinson  2.6   2.2   .84      .90   Maurice Cheeks  7.0   6.3   17
24   Mookie Blaylock 6.4   5.6   .87      .904   average         

These 47/48 players are above avg in the 'extra' assists in home playoff games, or in the % of their assists which are 'extras' at home.
At .947, Stockton is #70 of 90 in away/home ratio. In the Stockton era, in playoffs, the Jazz averaged 36.1 FG at home and 35.0 on the road, a .969 ratio.

13 of 90 have higher Ast/36 on the road; led by Vlade Divac, Derrick McKey, and Dwyane Wade.