Why EMPSAME is NIU in the monthly CPS MARCH-1994?

#1

Why EMPSAME is NIU in the monthly CPS MARCH-1994?

Also, there are many observations NIU in other years/months, while they clearly should be in the universe of the variable (I am considering empstat to measure employment):

[All]: Employed persons not in month-in-sample 1 or 5, and were employed last month.

This pattern is increasing over time. Does anyone know why?

#2

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