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Aging Patterns

April 24, 2017
 2017-22

Aging Patterns

 

              The 26-year-old hitters in my study hit 10,409 triples, which is 1,138 triples more than expected.   +1,138.    At age 27 they drop to +463 in triples, at age 28 to +229, and at age 29, to -38.    By age 30, they hit 396 fewer triples than expected (-396), at age 31 -700, and by age 33 -857.  

              You may remember that last week I published a study in which I had compared each player’s RBI in each season to his career RBI, by finding the RBI per plate appearances for his career, and then projecting that onto his plate appearances in the season.    Luke Appling was +61 RBI in 1936, which is a record; not just RBI, but I also did this for runs, hits, doubles, triples, walks, home runs, hit by pitch, grounding into double play, sacrifice hits and flies, and some other things.   I should also repeat the ground rules:   I didn’t include active players or 19th century players, and I didn’t include 20th century seasons by 19th century players.  

              Even without including those—or pitchers—I did have a very large number of players included in the study, which is kind of the whole point.    At the age of 26 there are 4,052 players included in the study.     It’s a big number.    They bat 250 times apiece, you’ve got a million at bats there.    It’s enough to make pretty good measurements of how skills change over time. 

              Let’s start with the raw totals, not that that is going to tell us a hell of a lot.   These are the raw totals of the players in the study, at each age:

 

Age

Count

G

AB

R

H

2B

3B

HR

RBI

16

3

51

154

18

25

4

0

0

8

17

22

331

877

78

182

17

8

4

71

18

89

1717

4185

480

990

151

46

35

379

19

243

6843

19979

2355

4913

735

188

248

1932

20

560

19649

61540

7709

16035

2538

653

974

6685

21

1130

53689

172144

21976

45035

7211

1992

2757

18910

22

1871

107321

343960

44091

89958

14547

3792

6210

38814

23

2678

169882

545466

71658

144279

23853

5740

10738

62996

24

3464

241444

769564

101051

203634

34126

7746

15499

90660

25

3908

299138

950138

126207

252872

42685

9190

19766

113017

26

4052

331943

1060892

141911

284137

48560

10409

22388

127279

27

3935

339182

1089000

145928

292265

50253

10058

23378

132451

28

3715

325701

1043615

138584

280184

48861

9309

22600

128156

29

3333

301285

971106

130424

262014

45465

8454

21754

120712

30

2997

276693

891466

119447

239408

41677

7501

19748

111235

31

2585

238815

765778

102539

206274

36542

6130

17391

96510

32

2211

201149

639094

85546

171740

29947

4858

14887

81184

33

1855

166507

529914

69864

142470

25099

4003

12376

67534

34

1509

130762

409118

54365

110094

19150

2935

9827

52919

35

1160

99227

306000

40328

82456

14403

2013

7587

40374

36

820

69900

213229

27781

57087

10044

1422

5353

28326

37

567

47093

142775

18700

38437

6807

823

3648

18878

38

375

30036

90472

11527

23974

4203

521

2213

11620

39

235

18311

54360

7062

14453

2591

286

1473

7238

40

146

11165

33285

4348

8936

1573

183

858

4393

41

88

6338

17760

2164

4635

783

107

407

2278

42

55

2999

7503

944

1891

305

47

186

955

 

              And, of course, there are some players who played at age 43, 44, etc., but we’re losing meaningful numbers, drifting into random occurrences.   Don’t ask me why I included the totals for 16-year-olds, but not for 43-year-olds.    Anyway, everything peaks at age 27 except triples and the count of players.   The count and triples peak at age 26.   27-year-olds in the study had 292,000 hits.   Just love those big numbers.  Continuing:

 

Age

BB

SO

SB

CS

Avg

1B

EBH

TB

GIDP

16

8

18

0

0

.162

21

4

29

3

17

44

136

13

2

.208

153

29

227

9

18

281

573

62

21

.237

758

232

1338

48

19

1442

2615

315

156

.246

3742

1171

6768

285

20

4910

7844

1189

495

.261

11870

4165

22801

812

21

14153

21927

4045

1492

.262

33075

11960

64501

2392

22

29772

45496

7573

2809

.262

65409

24549

130719

5050

23

48851

74153

12650

5070

.265

103948

40331

211826

8562

24

69833

104546

17463

6849

.265

146263

57371

299749

12475

25

87667

126121

21226

8287

.266

181231

71641

373235

15907

26

99591

139521

23473

9602

.268

202780

81357

420679

17518

27

104122

140696

23216

9065

.268

208576

83689

432768

18716

28

102809

133510

21361

8828

.268

199414

80770

415463

18163

29

96391

122943

18724

7601

.270

186341

75673

389649

17069

30

90033

111907

16383

6732

.269

170482

68926

355331

16305

31

78062

96699

13618

5454

.269

146211

60063

307249

14074

32

66675

81921

10947

4511

.269

122048

49692

256064

12156

33

55260

67909

8179

3549

.269

100992

41478

212703

10116

34

43354

53580

6156

2718

.269

78182

31912

164595

8277

35

32885

40129

4297

1932

.269

58453

24003

123646

6458

36

23398

28058

2869

1334

.268

40268

16819

86034

4450

37

15852

19114

1897

837

.269

27159

11278

57834

3078

38

10064

12108

1228

518

.265

17037

6937

35858

1966

39

6357

7329

674

312

.266

10103

4350

22035

1228

40

3718

4434

475

227

.268

6322

2614

13449

717

41

2189

2480

217

118

.261

3338

1297

6853

422

42

1053

1076

94

44

.252

1353

538

2848

180

 

              Stolen Bases and Caught Stealing also peak at age 26, and batting average peaks at age 29.  Everything else peaks at 27.   1B is singles; EBH is Extra Base Hits.    In the chart below "RB" is "Reached Base", which is the sum of Hits, Walks and Hit By Pitch:

 

Age

HBP

IBB

RB

SAC

SF

OUTS

PA

OBA

SPct

OPS

16

0

0

33

6

0

138

168

.204

.188

.392

17

0

3

229

17

1

724

942

.248

.259

.506

18

2

23

1294

61

7

3332

4557

.288

.320

.608

19

117

41

6472

312

46

15865

21896

.300

.339

.639

20

361

220

21306

1063

224

48099

68098

.318

.371

.688

21

1131

626

60319

2800

692

134485

190920

.321

.375

.695

22

2301

1390

122031

5627

1456

268944

383114

.323

.380

.703

23

3714

2593

196844

8384

2530

425733

608945

.328

.388

.716

24

5320

3906

278846

11512

3737

600503

860028

.329

.390

.718

25

6768

5016

347307

13909

4862

740231

1063344

.331

.393

.724

26

7621

5943

391348

15449

5456

824780

1189042

.333

.397

.730

27

7926

6269

404323

15821

5900

846237

1222775

.335

.397

.732

28

7539

6252

390532

14704

5722

810848

1174395

.337

.398

.735

29

7118

5969

365523

13377

5417

752556

1093410

.338

.401

.740

30

6601

5296

336042

12172

4912

692179

1005194

.338

.399

.737

31

5561

4728

289897

9978

4443

593453

863831

.340

.401

.741

32

4533

4137

242948

8004

3803

495828

722115

.340

.401

.741

33

3796

3388

201526

6685

3269

411063

598936

.340

.401

.742

34

2943

2710

156391

4750

2506

317275

462675

.342

.402

.744

35

2128

2100

117469

3415

1989

237338

346426

.342

.404

.747

36

1579

1515

82064

2367

1419

165712

241996

.342

.403

.746

37

1152

1080

55334

1463

968

110684

162113

.344

.405

.750

38

646

787

34684

861

625

70468

102669

.341

.396

.737

39

403

534

21213

496

386

42329

62002

.345

.405

.750

40

281

213

12864

294

235

25822

37742

.344

.404

.748

41

138

144

6932

157

114

13936

20328

.344

.386

.730

42

62

78

2983

37

50

5923

8682

.345

.380

.725

 

 

              As you can see, everything peaks at age 27 except on base percentage, slugging percentage and OPS, which continue to ascend slowly until age 37.  

              In fact, players do NOT hit better at age 37 than they do at age 37; that’s a statistical illusion.    There are two causes for this statistical illusion.   One is that, as players age, the best players stay in the pool whose skills are being measured, while the weaker players drop out of the major leagues, thus drop out of the pool.   At age 26 there are more than 4,000 players in the study.   At age 37 there are 567.   86% have dropped out.    

              And, of course, it is the best players who play until they are 37.    The players who are still playing at age 37 are the Willie Mayses, the Mickey Mantles, the Ty Cobbs and Babe Ruths and Stan Musials and Ted Williamses and David Ortizes and Joe Morgans and Mike Schmidts and George Bretts and Barry Bondses, plus a certain number of players who are not great players but who age exceptionally well.  

              The second reason for the illusion that older players hit a little bit better is that the floor is rising on the group.   The "floor" is the effect of defensive ability.   With the exception of Designated Hitters, each player has to have a certain level of defensive ability to stay in the lineup.   Defensive skill peaks earlier than hitting skill, and dissipates more rapidly.    A shortstop, let’s say Andrelton, might be so brilliant defensively that even if he has a .600 OPS, he can stay in the lineup.    If you are not a brilliant defensive player, you cannot stay in the lineup with a .600 OPS. 

              As players lose defensive skill in aging, they have to hit more to stay in the lineup.   All the players are being "cut off" once their OPS drops below X, with X being a different number for each player.   But the AVERAGE X increases with age.  

              As a result of these two factors—the dropping out of the weaker hitters, and the fact that the level of offensive skill required to avoid being eliminated from the sample is increasing—the average OPS of all hitters can increase and will increase with age, even if every single hitter in the study gets a little bit worse every year.    If every player loses three points off his OPS every year, but all those below a .650 OPS are eliminated from the study, and then the .650 increases by 4 points a year, then the average OPS will increase, even though every player’s OPS is declining.

              I have known THAT since at least 1980, but when I wrote about these issues in the 1980s I did not have the ability to make some of the adjustments that I needed to make.   Now I do.   That’s what this article is about.  

              We know that Cecil Fielder in 1990 was 26 years old, and we know that he hit 51 home runs that season.    We know that that is 14.9 home runs above his expectation, based on his career numbers.   It is 51 over 36.1, or 41% over expectation.    We have these numbers for all 26-year-old players.     This chart compares the performance of 26 year old hitters to their expectation, based on career performance:

 

Age

Count

G

AB

R

H

2B

3B

HR

RBI

26

4052

331943

1060892

141911

284137

48560

10409

22388

127279

26

 

-9543

1209

4372

4893

998

1138

528

1245

 

   

 

 

 

 

   

 

 

BB

SO

SB

CS

Avg

1B

EBH

TB

GIDP

 

99591

139521

23473

9602

.268

202780

81357

420679

17518

 

-1539

-3324

2838

1103

 

2230

2663

9750

-1027

 

 

 

 

 

 

 

 

 

 

 

HBP

IBB

RB

SAC

SF

OUTS

PA

 

 

 

7621

5943

391348

15449

5456

824780

1189042

 

 

 

133

165

3505

390

-234

-3452

0

 

 

 

              26-year-old hitters hit 10,409 triples, which is 1,138 more than expected.    We can calculate, then, that their EXPECTED triples were 9,271.   This version of the chart adds the expected number in each category:

 

Age

Count

G

AB

R

H

2B

3B

HR

RBI

26

4052

331943

1060892

141911

284137

48560

10409

22388

127279

26

 

-9543

1209

4372

4893

998

1138

528

1245

 

 

341486

1059683

137539

279244

47562

9271

21860

126034

 

     

 

 

 

 

 

 

 

BB

SO

SB

CS

Avg

1B

EBH

TB

GIDP

 

99591

139521

23473

9602

.268

202780

81357

420679

17518

 

-1539

-3324

2838

1103

 

2230

2663

9750

-1027

 

101130

142845

20635

8499

.264

200550

78694

410929

18545

 

 

 

 

 

 

 

 

 

 

 

HBP

IBB

RB

SAC

SF

OUTS

PA

 

 

 

7621

5943

391348

15449

5456

824780

1189042

 

 

 

133

165

3505

390

-234

-3452

0

 

 

 

7488

5778

387843

15059

5690

828232

1189042

 

 

 

              We now know that the EXPECTED batting average, for this set of players, given the career batting average of each player in the sample and given the number of plate appearances that each player had, was .264.    The .268 batting average that these players had at age 26 is four points OVER expectation.   

              The overall batting average of 26-year-olds in the study is .268, and the overall batting average of 37-year-olds in the study is .269.   But the EXPECTED batting average of the 37-year-olds, given THAT set of players, was .280.    The actual batting average of the group has increased from .268 to .269, but the expected batting average, considering who the players were, has increased from .264 to .280.   This is what I did not know when I wrote about these issues in the 1980s.   I knew that this increase had occurred, but I had no way of measuring it.

              OK, continuing with the process.    26-year-old hitters hit 10,409 triple, whereas they were expected to hit a mere 9,271, the lazy bastards.    They over-achieved in the triples category, at age 26, by 12%.    We can represent that as 112; I’m sure I don’t have to explain that.   The chart below gives these numbers for each category of our study:

 

Age

Count

G

AB

R

H

2B

3B

HR

RBI

26

4052

331943

1060892

141911

284137

48560

10409

22388

127279

26

 

-9543

1209

4372

4893

998

1138

528

1245

 

 

341486

1059683

137539

279244

47562

9271

21860

126034

 

 

97

100

103

102

102

112

102

101

 

     

 

 

 

 

 

 

 

BB

SO

SB

CS

Avg

1B

EBH

TB

GIDP

 

99591

139521

23473

9602

.268

202780

81357

420679

17518

 

-1539

-3324

2838

1103

 

2230

2663

9750

-1027

 

101130

142845

20635

8499

.264

200550

78694

410929

18545

 

98

98

114

113

102

101

103

102

94

 

 

 

 

 

 

 

 

 

 

 

HBP

IBB

RB

SAC

SF

OUTS

PA

 

 

 

7621

5943

391348

15449

5456

824780

1189042

 

 

 

133

165

3505

390

-234

-3452

0

 

 

 

7488

5778

387843

15059

5690

828232

1189042

 

 

 

102

103

101

103

96

100

100

 

 

 

              OK, now we’re getting somewhere.    We now know that 26-year-old hitters overachieve in the triples category by 12%, which we represent as 112.    But at what age does the propensity to hit triples peak, and how rapidly does it decline after that peak?

              The age at which triples peak is 21, when they are 21% higher than career norms.   From age 21 to 26 they decline at a rate of about 2% per year.   After 26 they decline by more like 4% per season:

 

Age

3B

19

97

20

110

21

121

22

118

23

117

24

115

25

112

26

112

27

105

28

103

29

100

30

95

31

90

32

85

33

84

34

80

35

74

36

76

37

66

38

66

39

60

40

59

 

              Players up to age 28 hit more triples than their career norms.   From age 30 on, they hit less.  

              Of course, you would assume that this was true, but there is a difference between knowing something generally and knowing the specifics of it.   Knowing the specifics of it, we can answer questions like "How much more rapidly do catchers lose speed (lose triples) than other players?   Do outfielders lose speed less rapidly than infielders?   Do tall players lose speed more rapidly than short players?"    This chart adds doubles and home runs to the age progression chart above:

 

Age

2B

3B

HR

19

86

97

61

20

95

110

72

21

95

121

79

22

96

118

90

23

98

117

94

24

99

115

96

25

101

112

101

26

102

112

102

27

102

105

104

28

103

103

104

29

102

100

106

30

101

95

104

31

102

90

102

32

99

85

102

33

99

84

99

34

97

80

99

35

96

74

97

36

95

76

94

37

95

66

93

38

93

66

88

39

94

60

93

40

92

59

89

 

              So we can see then that the prime ages for triples are ages 20 to 28, for doubles, 25 to 31, and for home runs, 25 to 32.    This is new knowledge for me; I did not know these things with this level of precision before doing this study.   I assume that other students of the game have probably found the same things or very similar things before, but I do a poor job of following the research of others.    Let’s add runs and RBI:

 

Age

2B

3B

HR

R

RBI

19

86

97

61

91

79

20

95

110

72

95

88

21

95

121

79

97

92

22

96

118

90

99

95

23

98

117

94

101

97

24

99

115

96

102

99

25

101

112

101

103

101

26

102

112

102

103

101

27

102

105

104

103

102

28

103

103

104

101

102

29

102

100

106

102

102

30

101

95

104

101

102

31

102

90

102

100

101

32

99

85

102

99

100

33

99

84

99

96

99

34

97

80

99

96

99

35

96

74

97

94

99

36

95

76

94

91

97

37

95

66

93

91

96

38

93

66

88

87

94

39

94

60

93

87

96

40

92

59

89

85

95

 

                           

              RBI peak two years later than runs scored, as you would expect.   But at what age would you suppose the tendency to get hit by a pitch reaches its peak?   Just pointing out to you that you do not know the answer.      Grounding into a double play increases markedly with age; stolen bases decline from an early age.   You could have guessed that.   Young players hit more sacrifice bunts; veterans hit more sacrifice flies:

 

Age

SB

CS

SB Pct

GIDP

HBP

SAC

SF

19

94

110

92

90

102

100

56

20

101

106

97

84

103

112

76

21

119

109

105

88

106

107

84

22

112

102

105

90

103

108

87

23

117

113

102

91

101

106

89

24

118

111

103

93

101

105

91

25

115

109

102

95

102

104

95

26

114

113

100

94

102

103

96

27

109

105

102

98

101

102

102

28

106

108

99

99

100

100

102

29

101

99

101

99

100

99

104

30

94

97

99

104

100

98

102

31

91

92

100

103

99

96

105

32

87

91

98

107

96

94

107

33

78

85

96

107

96

97

108

34

75

82

95

111

96

93

103

35

71

79

95

113

93

93

107

36

65

77

92

112

97

96

107

37

62

70

94

113

107

93

106

38

57

64

95

115

94

88

105

39

52

63

90

119

101

92

105

40

55

73

86

118

114

93

106

 

              I probably highlighted the wrong part of the chart for GIDP.  For some reason Hit Batsmen are a young person’s trait, in general; I did not know that and would not have guessed it.    I might speculate that less experienced players occasionally fail to read a pitch, leading to more of these relatively rare events early in a career.

              Young hitters are asked to bunt more often.    You would expect that to be true, but the increase in Sacrifice Flies as players age is very interesting.   One might expect veteran players to have more sacrifice fly opportunities because they are used in more RBI situations, but the increase in Sac Flies as players age is far too large to result from RBI opportunities.   

              Let me try to explain.    Getting a fly ball when a fly ball is needed is a subset of a clutch skill, is it not?   If you can do that, you’re a clutch player.   A traditional insider, presented with this data, would say "Of course".     Of course a veteran player knows how to get the ball in the air in a situation where a fly balls means a run.   Anyone would know that.    But 99% of the old baseball accepted wisdom of this type turns out on examination not to be true or not to be meaningfully true—such as clutch hitting in general.   I’m not surprised that veteran players exceed expected sacrifice flies by 1% or 2%; that could be explained by player usage patterns and some small skill differential.   But I am VERY surprised that they exceed expectations (relative to career norms) by 5% to 7%.     That MAY indicate a clutch ability.   It may be that, in another generation, when we have the data organized to do this study, we may find that veteran players increase their batting average in clutch situations by some small amount, which we have been previously unable to document.   This may be the largest surprise of the study.

              Double plays by 41-year-olds actually exceed expectations by 32% (132), speaking of large numbers.   There’s a big change in that category as players age.    Double plays by age increase by about 2% per year, going from 84% to 119%.    Not that this is actually huge, or HUEGHE, as the Prez sez.   A player who grounds into 10 double plays a year as a 21-year-old can expect to ground into 15 as a 40-year-old.  

              Let’s see; what haven’t I done here?   Games and At Bats:

Age

Count

G

AB

19

 

109

103

20

 

105

102

21

 

103

101

22

 

101

101

23

 

99

101

24

 

99

100

25

 

98

100

26

 

97

100

27

 

97

100

28

 

98

100

29

 

98

100

30

 

99

100

31

 

100

100

32

 

102

100

33

 

103

100

34

 

105

100

35

 

108

100

36

 

110

100

37

 

111

100

38

 

113

100

39

 

116

100

40

 

118

100

 

              What the "Games" chart shows is that both young players and old players play more partial games, whereas players in their prime play more complete games.    If a player has a low number of plate appearances per game relative to his career, that causes the number of games per plate appearance to rise, which shows up as a higher number (over 100) in this chart.   Young players pinch run and are used as defensive replacements; old players pinch hit and are pulled out of the game for rest when the score is 6-2.   The "AB" column (above) just shows the share of plate appearances which result in a charged at bat.   To show REAL variation in that column you have to add a couple of decimals:

Age

Count

G

AB

19

 

109

102.87

20

 

105

101.72

21

 

103

101.42

22

 

101

100.86

23

 

99

100.61

24

 

99

100.40

25

 

98

100.22

26

 

97

100.11

27

 

97

99.98

28

 

98

99.81

29

 

98

99.77

30

 

99

99.72

31

 

100

99.73

32

 

102

99.68

33

 

103

99.66

34

 

105

99.68

35

 

108

99.68

36

 

110

99.51

37

 

111

99.62

38

 

113

100.00

39

 

116

99.88

40

 

118

100.44

 

              That’s kind of a preview of the "walks" column (BB), so let’s get to strikeouts and walks:

Age

BB

SO

19

73

115

20

82

109

21

85

108

22

90

106

23

93

103

24

95

101

25

97

99

26

98

98

27

100

98

28

102

98

29

102

98

30

103

99

31

103

99

32

104

101

33

104

101

34

104

103

35

104

104

36

105

104

37

104

106

38

101

107

39

101

108

40

97

109

 

              Walks increase with age up to the age of 36, although the increases after the age of 24 are just about 1% per year.    Strikeouts drop when a player is in his prime (25-31), but are higher both for young players and for old. 

              Now, the rate stats.    Batting average, on base percentage and slugging percentage all basically

              1) Reach maturity (100) at age 24,

              2) Are still at 100 at age 31,

              3) Increase slightly in the middle of that range, and

              4) Decline at about 1% per year after age 31.  

              On base and slugging peak a little bit later than batting average—one year later—because walks and homers peak at 36 and 29, respectively, offsetting the declines in batting average, which actually start at age 27.  

Age

Avg