First, did you check to see if both datasets are uniquely identified by the
time and id variable?
Second, did you sort the data set?
Thuy
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Danielle H Ferry
Sent: Friday, March 03, 2006 7:01 PM
To: StataList
Subject: st: Strange merge behavior
Dear Statalisters,
I wonder if anyone can explain to me the bizarre behavior I am getting on a
match merge. The master dataset is a panel (12 years), and the data is not
unique on the match variable (placefip). The using dataset contains just 2
variables: the match variable
(placefip) and another (macci), which is what I am after here. The using
dataset is unique on the match variable (placefip). There is a
1-1 correspondence btween placefip and macci in the using dataset.
When I merge on placefip, however, I get the result that macci differs by
year within placefip. For example:
. ta year macci if placefip==5553000, mi
| Center city
year | 1 . | Total
-----------+----------------------+----------
1990 | 12,818 0 | 12,818
1991 | 12,607 0 | 12,607
1992 | 12,437 0 | 12,437
1993 | 12,187 0 | 12,187
1994 | 11,749 0 | 11,749
1995 | 11,183 0 | 11,183
1996 | 11,237 0 | 11,237
1997 | 0 10,741 | 10,741
1998 | 0 11,002 | 11,002
1999 | 0 11,254 | 11,254
2000 | 0 11,150 | 11,150
2001 | 0 11,196 | 11,196
-----------+----------------------+----------
Total | 84,218 55,343 | 139,561
I don't see how this can be! (Please note that for placefip==5553000,
_merge==3 in all cases.) After the merge, macci should be constant within
placefip (and _merge==3), right? Perhaps I have been working at this too
long, and the answer is obvious. If so, I apologize. Can anyone please help?
Thanks,
Danielle H Ferry
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