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70

Table 4.10 Data on Housing Starts in Canada (1954-4 to 1982-4 Quarterly)"

54-4

28.73

101.8

3.92

66-2

29.11

185.8

2.73

55-1

29.83

103.3

4.25

29.83

191.0

2.44

31.22

107.4

4.42

32.95

186.9

2.38

32.61

113.7

4.63

67-1

30.04

190.3

2.29

30.47

110.8

4.90

43.53

193.5

2.14

56-1

31.34

117.2

4.63

42.41

194.5

2.13

32.42

118.3

5.16

35.87

194.0

2.39

30.56

116.8

4.64

68-1

46.34

197.4

2.83

22.01

121.7

4.09

48.37

202.6

2.70

57-1

17.75

122.8

3.12

42.49

208.0

2.40

29.41

122.5

2.79

51.00

209.1

2.53

28.76

118.8

2.96

69-1

66.32

211.7

2.93

30.39

121.8

3.47

54.51

213.2

3.42

58-1

36.67

121.5

3.71

47.52

218.1

4.06

41.27

124.2

3.38

41.58

218.0

4.09

36.18

123.2

3.04

70-1

40.85

218.3

4.25

37.46

127.7

3.07

34.54

220.4

3.77

59-1

32.99

127.2

3.42

44.43

222.4

3.29

32.49

128.8

4.52

60.78

221.7

3.62

32.98

128.4

4.87

71-1

49.18

227.8

3.36

33.32

131.5

4.59

55.81

233.3

3.76

60-1

21.95

133.4

4.41

57.23

239.8

2.97

23.54

130.5

4.52

59.27

242.0

2.02

27.05

133.3

4.54

72-1

62.12

243.8

1.93

27.34

133.8

4.55

62.08

250.5

1.68

61-1

31.90

132.5

4.54

60.51

249.2

1.60

29.88

137.1

4.36

57.25

257.7

1.05

30.07

135.1

4.47

73-1

62.39

264.7

0.88

27.39

141.5

4.45

68.25

267.2

1.65

62-1

30.58

143.3

4.34

65.32

267.0

1.92

31.97

143.3

4.05

62.45

278.1

1.46

31.53

148.4

4.38

74-1

68.48

280.6

1.21

28.36

148.2

3.96

62.68

279.6

2.34

63-1

31.94

148.2

3.72

50.43

274.5

2.50

32.78

150.1

3.63

40.33

281.5

1.37

34.97

157.1

3.84

75-1

37.28

278.9

-0.96

39.12

157.7

3.85

51.37

280.4

-1.23

64-1

42.82

160.7

3.75

60.49

282.7

-0.09

32.84

162.2

3.69

67.14

286.8

0.78

37.40

165.2

3.81

76-1

66.58

294.4

1.42

46.10

166.6

3.90

70.57

298.9

1.87

65-1

40.63

169.9

3.68

64.94

299.0

2.54

38.23

172.4

3.47

63.81

299.0

2.88

39.63

177.0

3.34

77-1

53.48

301.3

2.36

40.38

179.0

3.28

61.83

302.5

1.65

66-1

41.12

183.4

3.17

61.79

304.9

0.71



Table 4.10 (Cont.)

77-4

59.81

307.9

0.54

80-3

41.39

2.69

78-1

69.51

310.5

0.59

40.57

332.6

4.97

50.31

312.7

1.62

81-1

39.14

332.0

7.53

55.22

318.4

2.28

53.69

338.5

8.56

53.05

318.9

4.00

47.06

338.3

11.37

79-1

46.19

322.5

4.28

33.87

335.5

8.00

48.53

322.3

3.73

82-1

40.71

319.8

6.27

48.29

324.6

3.85

28.61

320.9

7.41

49.24

328.1

5.85

25.43

322.4

6.26

80-1

38.24

325.6

6.00

32.20

316.6

3.12

35.33

321.3

5.26

"T, year and quarter; HS, housing starts; y, gross national expenditures (in 1971 $); RR, estimated real interest rate.

Source: R. Davidson and J. G. MacKinnon, "Testing Linear and Log-Linear Regressions Against Box-Cox Alternatives," Canadian Journal of Economics, August 1985, Table 5, pp. 515-516. Data on HS and have been rounded to four-digit numbers.

Table 4.11 Wages, Benefits, Unemployment, and Net National Product: United Kingdom, 1920-1938

Year

Weekly Wages, W(s.)

Weekly Benefits, is.)

Unemployment Rate (%)

BenefitsI Wages

NNP, e°

(£ million at 1938 factor cost)

1920

73.8

11.3

0.15

3426

1921

70.6

16.83

17.0

0.24

3242

1922

59.1

22.00

14.3

0.37

3384

1923

55.5

22.00

11.7

0.40

3514

1924

56.0

23.67

10.3

0.42

3622

1925

56.4

27.00

11.3

0.48

3840

1926

55.8

27.00

12.5

. 0.48

3656

1927

56.2

27.00

0.48

3937

1928

55.7

27.67

10.8

0.50

4003

1929

55.8

28.00

10.4

0.50

4097

1930

55.7

29.50

16.1

0.53

4082

1931

54.9

29.54

21.3

0.54

3832

1932

54.0

27.25

22.1

0.50

3828

1933

53.7

27.25

19.9

0.51

3899

1934

54.3

28.6

16.7

0.53

4196

1935

55.0

30.3

15.5

0.55

4365

1936

56.1

32.00

13.1

0.57

4498

1937

57.2

32.00

10.8

0.56

4665

1938

58.9

32.75

12.9

0.56

4807

°NNP, net national product; s., shilling =



Heteroskedasticity

5.1 Introduction

5.2 Detection of Heteroskedasticity

5.3 Consequences of Heteroskedasticity

5.4 Solutions to the Heteroskedasticity Problem

5.5 Heteroskedasticity and the Use of Deflators

*5.6 Testing the Linear Versus Log-Linear Functional Form Summary Exercises

Appendix to Chapter 5

5.1 Introduction

One of the assumptions we have made until now is that the errors u, in the regression equation have a common variance cr. This is known as the homo-skedasticity assumption. If the errors do not have a constant variance we say they are heteroskedastic. There are sesveral questions we might want to ask if the errors do not have a constant variance. These are:

1. How do we detect this problem?

2. What are the consequences on the properties of the least squares estimators, and what are the consequences on the estimated standard errors if we use OLS?

3. What are the solutions to this problem?



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