st: Need help with glcurve

[Stata Stata <statalearner@gmail.com>]

Hi,

I am working with grouped data on longitudinal form. I want to draw a
concentration curve using glcurve (or so I think).

What I've got so far is:

glcurve health, glvar(yord) pvar(rank) sortvar(income) replace
by(year) split lorenz nograph

where health is a binomial variable (with 0 for absent morbidity and 1
for morbidity) and
income is a number from 1-14 for different income groups.
Year is also a binomial variable (with 0 for the year 2007 and 1 for
the year 2009)

Then I use twoway to draw the curve, but the graph doesn't look right
to me. The lines for the two years I'm working with look like steps,
with the line of equality in the middle.

Am I doing something wrong? Should I be using a frequency weight and
if so, how do I create it?

Best regards,
Maria Erla
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