Table 1 Descriptive statistics of the variables used

1980

Mean

11.778

454,155.924

168,126.344

1.285

1996

Mean

16.480

800,107.820

293,405.006

3.029

std

47.038

1,739,488.751

569,685.039

2.755

std

67.353

2,638,400.956

959,456.060

5.725

1981

Mean

12.127

471,044.931

169,846.094

1.197

1997

Mean

16.740

823,545.680

302,636.873

3.234

std

48.979

1,804,086.629

580,843.148

2.265

std

68.243

2,725,033.235

998,472.927

7.221

1982

Mean

12.426

481,561.559

169,356.021

1.270

1998

Mean

16.995

848,505.233

306,063.612

3.606

std

50.617

1,842,351.213

570,649.219

2.858

std

69.108

2,830,602.354

1,028,573.363

7.180

1983

Mean

12.683

468,443.433

173,061.125

1.635

1999

Mean

17.260

874,721.487

317,639.343

4.577

std

51.961

1,787,124.221

591,469.221

2.807

std

69.926

2,945,857.958

1,074,286.878

7.804

1984

Mean

12.999

468,281.630

181,575.919

1.409

2000

Mean

17.558

910,560.729

334,719.195

5.628

std

53.319

1,794,357.103

634,239.635

2.977

std

70.826

3,079,126.069

1,126,005.233

10.032

1985

Mean

13.334

474,792.230

187,269.560

1.628

2001

Mean

17.841

942,183.470

340,233.218

4.978

std

54.678

1,823,285.219

658,474.221

3.506

std

71.793

3,216,026.326

1,143,081.335

9.617

1986

Mean

13.671

496,725.367

194,929.618

1.752

2002

Mean

18.117

972,784.272

348,121.142

5.606

std

55.936

1,890,802.076

682,741.112

3.925

std

72.788

3,344,003.740

1,165,718.655

10.043

1987

Mean

14.000

517,069.651

203,732.140

2.438

2003

Mean

18.432

1,025,260.303

358,278.790

4.599

std

57.065

1,950,505.109

707,574.290

4.794

std

73.714

3,505,394.653

1,205,161.938

9.295

1988

Mean

14.343

542,888.825

212,644.927

2.482

2004

Mean

18.809

1,115,236.401

376,384.210

4.635

std

58.494

2,024,926.264

737,002.408

5.775

std

74.864

3,765,697.494

1,258,918.758

9.762

1989

Mean

14.701

567,677.451

219,678.706

2.569

2005

Mean

19.101

1,228,107.151

398,768.660

5.328

std

60.361

2,092,597.704

761,853.568

5.488

std

75.649

4,114,511.020

1,317,702.953

11.114

1990

Mean

15.062

598,391.882

228,252.970

3.204

2006

Mean

19.449

1,362,797.584

414,236.223

4.737

std

62.023

2,153,172.393

780,555.343

6.204

std

76.563

4,509,109.447

1,370,650.023

9.209

1991

Mean

15.321

616,338.768

233,729.672

3.241

2007

Mean

19.802

1,462,579.240

433,107.615

4.467

std

63.383

2,183,997.256

787,548.430

6.268

std

77.473

4,770,668.327

1,425,377.191

7.398

1992

Mean

15.549

635,992.718

244,081.059

2.343

2008

Mean

20.095

1,552,115.359

440,736.543

4.248

std

64.249

2,216,966.358

818,800.869

4.806

std

78.203

5,019,146.147

1,444,895.526

7.040

1993

Mean

15.750

671,855.674

254,104.209

2.723

2009

Mean

20.265

1,579,023.191

441,339.897

3.839

std

65.083

2,309,684.885

850,061.215

6.276

std

78.840

5,115,717.649

1,436,698.346

6.545

1994

Mean

16.011

714,960.881

266,518.840

2.781

2010

Mean

20.570

1,623,685.784

463,966.400

4.088

std

65.862

2,421,837.193

889,099.612

5.620

std

79.588

5,287,237.525

1,507,251.764

6.901

1995

Mean

16.210

767,889.398

280,462.926

2.766

2011

Mean

20.873

1,713,752.560

479,023.024

3.898

std

66.541

2,565,239.496

923,961.730

4.837

std

80.302

5,658,061.263

1,567,260.611

6.750