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Re: st: running simple regression on mixed data of cross-section and panel


From   Melaku Fekadu <melaku.fekadu@GMAIL.COM>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: running simple regression on mixed data of cross-section and panel
Date   Tue, 7 Dec 2010 11:58:23 +0200

Hi Steven,

Thanks again

The weight of each individual is provided with the data and it takes
into account the fact that some respondents are recurring. In other
words, the weight for each individual is given so that the pooled
sample remains representative. No problem with weighting samples.

My questin is just what do you do when some of the observations are
not independent to each other resulting from the recurrence of
individuals (87% of the sample appear twice and 12% appear once). And
this recurrence is not accidental?
In this case, does xtreg helps?


On Mon, Dec 6, 2010 at 8:29 PM, Steven Samuels <sjsamuels@gmail.com> wrote:
> Without going into the details of your particular data set, I urge you to
> consult the study documentation .  Weighting for such rotating studies
> really requires a very clear definition about what population each
> individual represents. You might well have to construct new weights to do
> your analysis.  Perhaps the study documentation ,or publications based on
> the survey, will provide guidance; Otherwise, you will need to write to the
> survey organization for advice.
>
> Steve
>
> Steven J. Samuels
> sjsamuels@gmail.com
> 18 Cantine's Island
> Saugerties NY 12477
> USA
> Voice: 845-246-0774
> Fax:    206-202-4783
>
> On Dec 6, 2010, at 1:12 PM, Melaku Fekadu wrote:
>
> Hi Steve,
>
> Thanks for your help and here is a detail about the survey structure.
>
> The labor force survey is quarterly. In a given quarter, no individual
> appears more than once in the data. It is representative of the entire
> population and employment figures can be drawn from it.
>
> The survey returns to the same individuals in the subsequent quarters
> to be able to follow up their employment situation.  The panel has a
> rotating structure: not all panels start at the same time. An example
> is given below. All in all, an individual should be interviewed in 4
> quarters: in the first two consecutive quarters and in two more
> quarters after a spell of two quarters (with no interviews conducted)
> in between.
>
> For example, focusing about individuals who are interviewed in Q1
> 2009, as seen under Q1 bellow, they are composed of four types of
> individuals:
>
> 1) those who completed their final (fourth) interview in Q1. These
> individuals did their last 3 interviews in previous years
> 2) those who do their third interview in Q1. These individuals will do
> their final (fourth) interview in the next quarter, Q2, this year.
> They did their last 2 interviews in previous years.
> 3) those who do their second interview in Q1. These individuals will
> have a spell of 2 quarters (Q2 and Q3) with no interviews and will do
> their third interview in Q4, this year. They will do their last
> interview in Q1 of next year, 2010.
> 4) those who are interviewed for the first time in Q1. These
> individuals will do their second interview in Q2, this year. They will
> take a spell of two quarters (Q3 and Q4) with no interviews conducted.
> And then they will do their third and fourth interviews in the Q1 and
> Q2 of next year, 2010.
>
> Individuals who are interviewed in the other quarters of 2009 are also
> composed of four types of individuals with similar features.
>
> The problem of recurring individuals arises when I use a pooled data
> from 4 quarters. As we see the recurrence of respondents is not
> accidental. As seen bellow only 2/16 or 12.5% of the observations in
> the pooled data appear only once (those who are interviewed in Q1
> their last – fourth – interview, and those who are interviewed in Q4
> their first interview). The rest 87.5% appear twice.
>
> I would like to do my regressions in the pooled data of four quarters
> and I am afraid that this recurring feature of individuals has an
> impact on my regressions. My question is how do I take care of it?
> Does 'xtreg' helps? If so, I would appreciate any help on how to use
> xtreg.
>
> Year=2009
> Q1      Q2        Q3      Q4
>
> 4
> 3        4
>        3        4
>                 3        4
> 2                          3
> 1       2
>       1         2
>                 1        2
>                          1
>
>
>
>
> On Sun, Dec 5, 2010 at 12:38 AM, Steven Samuels <sjsamuels@gmail.com> wrote:
>>
>> --
>>
>> A panel survey is one which deliberately resurveys the same units. My
>> guess
>> is that you are talking about repeated independent samples of a population
>> at different times. If not, please provide more details.  If so, the
>> chance
>> appearance of  individuals in more than one survey is not an issue.  Use
>> Stata survey commands, and incorporate "survey occasion" into the stratum
>> definition for the -svyset- command.  For most repeated surveys, the study
>> documentation will give advice about this kind of issue.
>>
>> Steve
>>
>> Steven J. Samuels
>> sjsamuels@gmail.com
>> 18 Cantine's Island
>> Saugerties NY 12477
>> USA
>> Voice: 845-246-0774
>> Fax:    206-202-4783
>>
>> On Dec 3, 2010, at 2:35 PM, Melaku Fekadu wrote:
>>
>> Dear all,
>>
>>
>> I want to do a regression of employment (logistic) and wage
>> (loglinear) on some demographic variables. I do the regressions on a
>> cross-section data of labor force survey. However, small proportion of
>> individuals in the data recur more than once.
>>
>>
>> How do I take into account the fact some people appear more than once
>> in the data. Do I have to be concerned from running a simple
>> regression?
>>
>>
>> Thanks
>> fekadu,
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