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st: Suggestions On Event Study Implementation Using Sureg
From |
"Thomas Jacobs" <[email protected]> |
To |
StataList <[email protected]> |
Subject |
st: Suggestions On Event Study Implementation Using Sureg |
Date |
Mon, 3 Nov 2008 17:03:05 -0600 |
I am attempting to use seemingly unrelated regression to perform an
event study. I have generated an indicator variable (EventIndicator)
which will be 1 for the event days and zero for the observation period
and I will perform sureg on the joint observation/event period and
rely upon this indicator to infer whether the event is statistically
significant. However, no matter how I have performed this, the
indicator variable is always dropped. Is this by design and if so, is
there a workaround? I have experimented with pooled OLS and found
that some combinations of observation period and event length are
statistically significant across the population. Here is the code:
scalar EventBegin = 1381
scalar EventEnd = 1382
scalar ObservationPeriod = 250
keep if TradeDateNum >= EventBegin - ObservationPeriod
keep if TradeDateNum <= EventEnd
gen EventIndicator = 0
replace EventIndicator = 1 if TradeDateNum >= EventBegin
egen Companies=group(CompanyNum)
summ Companies
local Count = r(max)
reshape wide CompanyNum LnRtStock LnRtFiveYrMid, i(TradeDateNum) j(Companies)
tsset TradeDateNum
forvalues i=1/`Count'{
local eqn "`eqn' (LnRtFiveYrMid`i' L(1/2).LnRtFiveYrMid`i'
L(0/4).LnRtCDX LnRtCMT LnRtTED L(0/2).LnRtStock`i' EventIndicator) "
}
sureg `eqn'
subset of output:
LnRtFiveY~53 |
LnRtFiveY~53 |
L1. | -.0885171 .0644396 -1.37 0.170 -.2148164 .0377822
L2. | .079153 .0660569 1.20 0.231 -.0503161 .2086222
LnRtCDX |
--. | .4928492 .1769154 2.79 0.005 .1461013 .8395971
L1. | .5052867 .1681416 3.01 0.003 .1757353 .8348381
L2. | -.0757411 .1695676 -0.45 0.655 -.4080875 .2566054
L3. | -.0068345 .1546976 -0.04 0.965 -.3100362 .2963672
L4. | .2961546 .152511 1.94 0.052 -.0027615 .5950707
LnRtCMT | .4458879 .5702881 0.78 0.434 -.6718563 1.563632
LnRtTED | -.0258378 .1162406 -0.22 0.824 -.2536653 .2019897
LnRtStock53 |
--. | -.4131414 .2793668 -1.48 0.139 -.9606904 .1344075
L1. | -.4063891 .2707067 -1.50 0.133 -.9369645 .1241862
L2. | -.1351143 .2763632 -0.49 0.625 -.6767762 .4065476
EventIndic~r | (dropped)
_cons | .0102328 .0081974 1.25 0.212 -.0058339 .0262995
-------------+----------------------------------------------------------------
LnRtFiveY~54 |
LnRtFiveY~54 |
L1. | -.0494574 .0610598 -0.81 0.418 -.1691324 .0702177
L2. | -.0112287 .0596863 -0.19 0.851 -.1282116 .1057543
LnRtCDX |
--. | .1646653 .1218418 1.35 0.177 -.0741403 .403471
L1. | .398986 .1132175 3.52 0.000 .1770838 .6208883
L2. | -.0147374 .1156556 -0.13 0.899 -.2414183 .2119435
L3. | .2433624 .1105843 2.20 0.028 .0266213 .4601036
L4. | -.03803 .1070395 -0.36 0.722 -.2478235 .1717636
LnRtCMT | -.2296451 .3975347 -0.58 0.563 -1.008799 .5495085
LnRtTED | -.1605888 .0809712 -1.98 0.047 -.3192893 -.0018882
LnRtStock54 |
--. | -1.023552 .1489326 -6.87 0.000 -1.315454 -.7316491
L1. | -.7757145 .1556815 -4.98 0.000 -1.080845 -.4705844
L2. | -.4211249 .1672822 -2.52 0.012 -.7489921 -.0932577
EventIndic~r | (dropped)
_cons | -.005541 .005701 -0.97 0.331 -.0167148 .0056327
Thanks for any suggestions anyone might have.
Tom
--
Thomas Jacobs
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