1980

1981

1982

1983

1984

1985

1986

3,396

3,356

3,444

3,338

3,399

3,313

3,369

2,440

2,383

2,417

2,224

2,315

2,192

2,197

956

973

1,027

1,114

1,084

1,121

1,172

2,905

2,898

2,927

2,854

2,868

2,727

2,751

147

125

114

108

109

113

118

273

248

294

291

308

364

343

71

85

109

85

114

109

157

83

91

94

86

99

104

119

1,362

1,364

1,385

1,313

1,446

1,409

1,415

626

616

625

668

625

634

699

103

70

78

70

68

66

58

225

255

275

247

238

200

196

2,316

2,305

2,363

2,298

2,377

2,309

2,368

71.6%

72.3%

72.6%

72.1%

74.2%

73.8%

74.9%

891

865

860

851

791

790

759

29

20

31

37

34

28

36

3,236

3,190

3,254

3,186

3,202

3,127

3,163

6.5

6.5

6.67

7

7.09

7.17

7.25

6

6

6

6.17

6.33

6.42

6.41

29.25

29.33

29.59

29.83

30.25

30.42

30.59

1997

1998

1999

2000

2001

2002

2003

5,459

5,465

5,340

5,547

5,397

5,375

5,412

3,110

3,113

3,074

3,060

2,984

3,015

2,960

2,349

2,352

2,266

2,478

2,403

2,358

2,439

3,451

3,492

3,438

3,620

3,623

3,563

3,534

562

533

477

364

341

315

266

1,233

1,213

1,224

1,336

1,202

1,222

1,341

243

241

218

227

231

275

366

261

277

308

315

364

367

358

2,293

2,312

2,223

2,340

2,170

2,269

2,343

979

1,027

977

931

882

884

932

87

69

75

148

102

109

172

193

250

476

362

387

273

311

3,552

3,658

3,751

3,781

3,541

3,535

3,758

71.1%

73.0%

75.8%

73.6%

71.0%

71.3%

75.0%

1,288

1,257

1,152

1,276

1,373

1,368

1,193

156

93

43

83

76

58

60

4,996

5,008

4,946

5,140

4,990

4,961

5,011

7.92

7.83

7.59

7.75

7.83

7.59

7.59

6.92

6.92

6.75

6.84

6.92

6.75

6.67

31

30.92

30.83

30.91

30.83

30.67

30.58



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement