关于如何在模型中加入季度时间固定效应以及季节性固定效应,很多人可能会困惑,傻傻分不清楚,这里作一下区分,一种是Quarterly time fixed effects,这是时间固定效应,我把它翻译成季度时间固定效应。另一种是Seasonal quarter fixed effects,我把它翻译成季节性固定效应。注意前者是我们常说的时间固定效应的一种。当然关于,这两种固定效应的中文翻译,大家可以留言讨论,我也不太确定这么翻译是否准确。下面看这两种固定效应究竟如何实现。
- * Example generated by -dataex-. To install: ssc install dataex
- clear
- input float company double(year_quarter year) byte quarter float(invest mvalue kstock)
- 1 -100 1935 1 317.6 3078.5 2.8
- 1 -99 1935 2 391.8 4661.7 52.6
- 1 -98 1935 3 410.6 5387.1 156.9
- 1 -97 1935 4 257.7 2792.2 209.2
- 1 -96 1936 1 330.8 4313.2 203.4
- 1 -95 1936 2 461.2 4643.9 207.2
- 1 -94 1936 3 512 4551.2 255.2
- 1 -93 1936 4 448 3244.1 303.7
- 1 -92 1937 1 499.6 4053.7 264.1
- 1 -91 1937 2 547.5 4379.3 201.6
- 1 -90 1937 3 561.2 4840.9 265
- 1 -89 1937 4 688.1 4900.9 402.2
- 1 -88 1938 1 568.9 3526.5 761.5
- 1 -87 1938 2 529.2 3254.7 922.4
- 1 -86 1938 3 555.1 3700.2 1020.1
- 1 -85 1938 4 642.9 3755.6 1099
- 1 -84 1939 1 755.9 4833 1207.7
- 1 -83 1939 2 891.2 4924.9 1430.5
- 1 -82 1939 3 1304.4 6241.7 1777.3
- 1 -81 1939 4 1486.7 5593.6 2226.3
- 2 -100 1935 1 209.9 1362.4 53.8
- 2 -99 1935 2 355.3 1807.1 50.5
- 2 -98 1935 3 469.9 2676.3 118.1
- 2 -97 1935 4 262.3 1801.9 260.2
- 2 -96 1936 1 230.4 1957.3 312.7
- 2 -95 1936 2 361.6 2202.9 254.2
- 2 -94 1936 3 472.8 2380.5 261.4
- 2 -93 1936 4 445.6 2168.6 298.7
- 2 -92 1937 1 361.6 1985.1 301.8
- 2 -91 1937 2 288.2 1813.9 279.1
- 2 -90 1937 3 258.7 1850.2 213.8
- 2 -89 1937 4 420.3 2067.7 132.6
- 2 -88 1938 1 420.5 1796.7 264.8
- 2 -87 1938 2 494.5 1625.8 306.9
- 2 -86 1938 3 405.1 1667 351.1
- 2 -85 1938 4 418.8 1677.4 357.8
- 2 -84 1939 1 588.2 2289.5 342.1
- 2 -83 1939 2 645.5 2159.4 444.2
- 2 -82 1939 3 641 2031.3 623.6
- 2 -81 1939 4 459.3 2115.5 669.7
- 3 -100 1935 1 33.1 1170.6 97.8
- 3 -99 1935 2 45 2015.8 104.4
- 3 -98 1935 3 77.2 2803.3 118
- 3 -97 1935 4 44.6 2039.7 156.2
- 3 -96 1936 1 48.1 2256.2 172.6
- 3 -95 1936 2 74.4 2132.2 186.6
- 3 -94 1936 3 113 1834.1 220.9
- 3 -93 1936 4 91.9 1588 287.8
- 3 -92 1937 1 61.3 1749.4 319.9
- 3 -91 1937 2 56.8 1687.2 321.3
- 3 -90 1937 3 93.6 2007.7 319.6
- 3 -89 1937 4 159.9 2208.3 346
- 3 -88 1938 1 147.2 1656.7 456.4
- 3 -87 1938 2 146.3 1604.4 543.4
- 3 -86 1938 3 98.3 1431.8 618.3
- 3 -85 1938 4 93.5 1610.5 647.4
- 3 -84 1939 1 135.2 1819.4 671.3
- 3 -83 1939 2 157.3 2079.7 726.1
- 3 -82 1939 3 179.5 2371.6 800.3
- 3 -81 1939 4 189.6 2759.9 888.9
- 4 -100 1935 1 40.29 417.5 10.5
- 4 -99 1935 2 72.76 837.8 10.2
- 4 -98 1935 3 66.26 883.9 34.7
- 4 -97 1935 4 51.6 437.9 51.8
- 4 -96 1936 1 52.41 679.7 64.3
- 4 -95 1936 2 69.41 727.8 67.1
- 4 -94 1936 3 68.35 643.6 75.2
- 4 -93 1936 4 46.8 410.9 71.4
- 4 -92 1937 1 47.4 588.4 67.1
- 4 -91 1937 2 59.57 698.4 60.5
- 4 -90 1937 3 88.78 846.4 54.6
- 4 -89 1937 4 74.12 893.8 84.8
- 4 -88 1938 1 62.68 579 96.8
- 4 -87 1938 2 89.36 694.6 110.2
- 4 -86 1938 3 78.98 590.3 147.4
- 4 -85 1938 4 100.66 693.5 163.2
- 4 -84 1939 1 160.62 809 203.5
- 4 -83 1939 2 145 727 290.6
- 4 -82 1939 3 174.93 1001.5 346.1
- 4 -81 1939 4 172.49 703.2 414.9
- 5 -100 1935 1 39.68 157.7 183.2
- 5 -99 1935 2 50.73 167.9 204
- 5 -98 1935 3 74.24 192.9 236
- 5 -97 1935 4 53.51 156.7 291.7
- 5 -96 1936 1 42.65 191.4 323.1
- 5 -95 1936 2 46.48 185.5 344
- 5 -94 1936 3 61.4 199.6 367.7
- 5 -93 1936 4 39.67 189.5 407.2
- 5 -92 1937 1 62.24 151.2 426.6
- 5 -91 1937 2 52.32 187.7 470
- 5 -90 1937 3 63.21 214.7 499.2
- 5 -89 1937 4 59.37 232.9 534.6
- 5 -88 1938 1 58.02 249 566.6
- 5 -87 1938 2 70.34 224.5 595.3
- 5 -86 1938 3 67.42 237.3 631.4
- 5 -85 1938 4 55.74 240.1 662.3
- 5 -84 1939 1 80.3 327.3 683.9
- 5 -83 1939 2 85.4 359.4 729.3
- 5 -82 1939 3 91.9 398.4 774.3
- 5 -81 1939 4 81.43 365.7 804.9
- 6 -100 1935 1 20.36 197 6.5
- 6 -99 1935 2 25.98 210.3 15.8
- 6 -98 1935 3 25.94 223.1 27.7
- 6 -97 1935 4 27.53 216.7 39.2
- 6 -96 1936 1 24.6 286.4 48.6
- 6 -95 1936 2 28.54 298 52.5
- 6 -94 1936 3 43.41 276.9 61.5
- 6 -93 1936 4 42.81 272.6 80.5
- 6 -92 1937 1 27.84 287.4 94.4
- 6 -91 1937 2 32.6 330.3 92.6
- 6 -90 1937 3 39.03 324.4 92.3
- 6 -89 1937 4 50.17 401.9 94.2
- 6 -88 1938 1 51.85 407.4 111.4
- 6 -87 1938 2 64.03 409.2 127.4
- 6 -86 1938 3 68.16 482.2 149.3
- 6 -85 1938 4 77.34 673.8 164.4
- 6 -84 1939 1 95.3 676.9 177.2
- 6 -83 1939 2 99.49 702 200
- 6 -82 1939 3 127.52 793.5 211.5
- 6 -81 1939 4 135.72 927.3 238.7
- 7 -100 1935 1 24.43 138 100.2
- 7 -99 1935 2 23.21 200.1 125
- 7 -98 1935 3 32.78 210.1 142.4
- 7 -97 1935 4 32.54 161.2 165.1
- 7 -96 1936 1 26.65 161.7 194.8
- 7 -95 1936 2 33.71 145.1 222.9
- 7 -94 1936 3 43.5 110.6 252.1
- 7 -93 1936 4 34.46 98.1 276.3
- 7 -92 1937 1 44.28 108.8 300.3
- 7 -91 1937 2 70.8 118.2 318.2
- 7 -90 1937 3 44.12 126.5 336.2
- 7 -89 1937 4 48.98 156.7 351.2
- 7 -88 1938 1 48.51 119.4 373.6
- 7 -87 1938 2 50 129.1 389.4
- 7 -86 1938 3 50.59 134.8 406.7
- 7 -85 1938 4 42.53 140.8 429.5
- 7 -84 1939 1 64.77 179 450.6
- 7 -83 1939 2 72.68 178.1 466.9
- 7 -82 1939 3 73.86 186.8 486.2
- 7 -81 1939 4 89.51 192.7 511.3
- 8 -100 1935 1 12.93 191.5 1.8
- 8 -99 1935 2 25.9 516 .8
- 8 -98 1935 3 35.05 729 7.4
- 8 -97 1935 4 22.89 560.4 18.1
- 8 -96 1936 1 18.84 519.9 23.5
- 8 -95 1936 2 28.57 628.5 26.5
- 8 -94 1936 3 48.51 537.1 36.2
- 8 -93 1936 4 43.34 561.2 60.8
- 8 -92 1937 1 37.02 617.2 84.4
- 8 -91 1937 2 37.81 626.7 91.2
- 8 -90 1937 3 39.27 737.2 92.4
- 8 -89 1937 4 53.46 760.5 86
- 8 -88 1938 1 55.56 581.4 111.1
- 8 -87 1938 2 49.56 662.3 130.6
- 8 -86 1938 3 32.04 583.8 141.8
- 8 -85 1938 4 32.24 635.2 136.7
- 8 -84 1939 1 54.38 723.8 129.7
- 8 -83 1939 2 71.78 864.1 145.5
- 8 -82 1939 3 90.08 1193.5 174.8
- 8 -81 1939 4 68.6 1188.9 213.5
- 9 -100 1935 1 26.63 290.6 162
- 9 -99 1935 2 23.39 291.1 174
- 9 -98 1935 3 30.65 335 183
- 9 -97 1935 4 20.89 246 198
- 9 -96 1936 1 28.78 356.2 208
- 9 -95 1936 2 26.93 289.8 223
- 9 -94 1936 3 32.08 268.2 234
- 9 -93 1936 4 32.21 213.3 248
- 9 -92 1937 1 35.69 348.2 274
- 9 -91 1937 2 62.47 374.2 282
- 9 -90 1937 3 52.32 387.2 316
- 9 -89 1937 4 56.95 347.4 302
- 9 -88 1938 1 54.32 291.9 333
- 9 -87 1938 2 40.53 297.2 359
- 9 -86 1938 3 32.54 276.9 370
- 9 -85 1938 4 43.48 274.6 376
- 9 -84 1939 1 56.49 339.9 391
- 9 -83 1939 2 65.98 474.8 414
- 9 -82 1939 3 66.11 496 443
- 9 -81 1939 4 49.34 474.5 468
- 10 -100 1935 1 2.54 70.91 4.5
- 10 -99 1935 2 2 87.94 4.71
- 10 -98 1935 3 2.19 82.2 4.57
- 10 -97 1935 4 1.99 58.72 4.56
- 10 -96 1936 1 2.03 80.54 4.38
- 10 -95 1936 2 1.81 86.47 4.21
- 10 -94 1936 3 2.14 77.68 4.12
- 10 -93 1936 4 1.86 62.16 3.83
- 10 -92 1937 1 .93 62.24 3.58
- 10 -91 1937 2 1.18 61.82 3.41
- 10 -90 1937 3 1.36 65.85 3.31
- 10 -89 1937 4 2.24 69.54 3.23
- 10 -88 1938 1 3.81 64.97 3.9
- 10 -87 1938 2 5.66 68 5.38
- 10 -86 1938 3 4.21 71.24 7.39
- 10 -85 1938 4 3.42 69.05 8.74
- 10 -84 1939 1 4.67 83.04 9.07
- 10 -83 1939 2 6 74.42 9.93
- 10 -82 1939 3 6.53 63.51 11.68
- 10 -81 1939 4 5.12 58.12 14.33
- end
- format %tq year_quarter
- format %ty year
- ***季度时间固定效应(Quarterly time fixed effects)
- reghdfe invest mvalue kstock,a(company year_q)
- HDFE Linear regression Number of obs = 200
- Absorbing 2 HDFE groups F( 2, 169) = 217.44
- Prob > F = 0.0000
- R-squared = 0.9517
- Adj R-squared = 0.9431
- Within R-sq. = 0.7201
- Root MSE = 51.7245
- ------------------------------------------------------------------------------
- invest | Coef. Std. Err. t P>|t| [95% Conf. Interval]
- -------------+----------------------------------------------------------------
- mvalue | 0.118 0.014 8.56 0.000 0.091 0.145
- kstock | 0.358 0.023 15.75 0.000 0.313 0.403
- _cons | -80.164 14.844 -5.40 0.000 -109.467 -50.860
- ------------------------------------------------------------------------------
- Absorbed degrees of freedom:
- ------------------------------------------------------+
- Absorbed FE | Categories - Redundant = Num. Coefs |
- --------------+---------------------------------------|
- company | 10 0 10 |
- year_quarter | 20 1 19 |
- ------------------------------------------------------+
- 那么在考虑季度时间固定效应后,能否继续控制year fixed effects呢?答案是否定的,因为year fixed effects会被季度时间固定效应所吸收。
- reghdfe invest mvalue kstock,a(company year_q year)
- HDFE Linear regression Number of obs = 200
- Absorbing 3 HDFE groups F( 2, 169) = 217.44
- Prob > F = 0.0000
- R-squared = 0.9517
- Adj R-squared = 0.9431
- Within R-sq. = 0.7201
- Root MSE = 51.7245
- ------------------------------------------------------------------------------
- invest | Coef. Std. Err. t P>|t| [95% Conf. Interval]
- -------------+----------------------------------------------------------------
- mvalue | 0.118 0.014 8.56 0.000 0.091 0.145
- kstock | 0.358 0.023 15.75 0.000 0.313 0.403
- _cons | -80.164 14.844 -5.40 0.000 -109.467 -50.860
- ------------------------------------------------------------------------------
- Absorbed degrees of freedom:
- ------------------------------------------------------+
- Absorbed FE | Categories - Redundant = Num. Coefs |
- --------------+---------------------------------------|
- company | 10 0 10 |
- year_quarter | 20 1 19 |
- year | 5 5 0 ?|
- ------------------------------------------------------+
- ? = number of redundant parameters may be higher
- 可以看到此时year dummies均被踢出去了。
- ***季节固定效应(Seasonal quarter fixed effects)
- reghdfe invest mvalue kstock,a(company quarter)
- HDFE Linear regression Number of obs = 200
- Absorbing 2 HDFE groups F( 2, 185) = 297.65
- Prob > F = 0.0000
- R-squared = 0.9442
- Adj R-squared = 0.9400
- Within R-sq. = 0.7629
- Root MSE = 53.1244
- ------------------------------------------------------------------------------
- invest | Coef. Std. Err. t P>|t| [95% Conf. Interval]
- -------------+----------------------------------------------------------------
- mvalue | 0.111 0.012 9.06 0.000 0.087 0.135
- kstock | 0.311 0.018 17.63 0.000 0.276 0.346
- _cons | -59.772 12.829 -4.66 0.000 -85.082 -34.463
- ------------------------------------------------------------------------------
- Absorbed degrees of freedom:
- -----------------------------------------------------+
- Absorbed FE | Categories - Redundant = Num. Coefs |
- -------------+---------------------------------------|
- company | 10 0 10 |
- quarter | 4 1 3 |
- -----------------------------------------------------+
- 那么假如季节性固定效应后,能否在继续控制year ficed effects吗?答案是Yes,此时季节性固定效应并不会吸收年度固定效应。
- reghdfe invest mvalue kstock,a(company quarter year)
- HDFE Linear regression Number of obs = 200
- Absorbing 3 HDFE groups F( 2, 181) = 213.47
- Prob > F = 0.0000
- R-squared = 0.9471
- Adj R-squared = 0.9418
- Within R-sq. = 0.7023
- Root MSE = 52.3196
- ------------------------------------------------------------------------------
- invest | Coef. Std. Err. t P>|t| [95% Conf. Interval]
- -------------+----------------------------------------------------------------
- mvalue | 0.111 0.013 8.61 0.000 0.085 0.136
- kstock | 0.356 0.023 15.72 0.000 0.311 0.400
- _cons | -71.774 14.088 -5.09 0.000 -99.572 -43.976
- ------------------------------------------------------------------------------
- Absorbed degrees of freedom:
- -----------------------------------------------------+
- Absorbed FE | Categories - Redundant = Num. Coefs |
- -------------+---------------------------------------|
- company | 10 0 10 |
- quarter | 4 1 3 |
- year | 5 1 4 ?|
- -----------------------------------------------------+
- ? = number of redundant parameters may be higher
关于季节时间固定效应以及季节固定效应,你分清了吗?当然你也可以在此基础上考虑季节性趋势以及季度时间趋势。此外,你也可以类比月度时间固定效应以及月份固定效应。当然还有月度时间趋势以及月份趋势。


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