st: Problem tracking students

["S. D'Souza" <smdsouza@gmail.com>]

Hi everyone,

I am working with a student level dataset that contains longitudinal
data in wide format (case by variables).  I am interested in 6th grade
students in 2002-03 only and the dataset has been limited to these
students. The total sample is 21,731 students.

The problem: I am interested in tracking students who drop out of the
sample over the next two years, but am having difficulty doing so. As
you can see in the table below, in 2003-04 (year 2), the sample drops
by 1,922 for a total of 19,809 students:


Grade level |

    2003-04 |

  180th day |      Freq.     Percent        Cum.

------------+-----------------------------------

          6 |        886        4.08        4.08

          7 |     18,833       86.66       90.74

          8 |         80        0.37       91.11

          9 |         10        0.05       91.16

          . |      1,922        8.84      100.00

------------+-----------------------------------

      Total |     21,731      100.00



In the following year, 2004-05 (year 3), the sample drops by 1,126 for
a total of 18,683 students:


Grade level |

    2004-05 |

  180th day |      Freq.     Percent        Cum.

------------+-----------------------------------

          6 |         14        0.06        0.06

          7 |      1,336        6.15        6.21

          8 |     17,207       79.18       85.39

          9 |        115        0.53       85.92

         10 |         10        0.05       85.97

         11 |          1        0.00       85.97

          . |      3,048       14.03      100.00

------------+-----------------------------------

      Total |     21,731      100.00


I would like to create flags for students who drop out in years 2 and
3 respectively. I am able to create a flag for the 1,922 students who
drop out in year 2 without any problem. However, the flag for year 3
shows that 1,381 students are being flagged instead of 1,126 students.
All of these 1,381 cases are verified in the data to have missing
values in year 3. Can someone please explain why my year 3 flag is
identifying more than 1,126 students?

Here is my code where “gr05_180” provides grade level in 2004-05 and
“gr04_180” provides grade level in 2003-04:

 gen gry3m=.

replace gry3m=1 if gr05_180==. & gr04_180!=. & cohort1==1


. tab gry3m



      gry3m |      Freq.     Percent        Cum.

------------+-----------------------------------

          1 |      1,381      100.00      100.00

------------+-----------------------------------

      Total |      1,381      100.00


 Thanks,

Stephanie

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