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I am trying to replicate the results in Bertrand, M., Duflo, E., Mullainathan, S., 2004. How Much Should We Trust Differences-In-Differences Estimates? The Quarterly Journal of Economics 119 (1). 249–275. On page 255 the authors state that

"We extract data on women in their fourth interview month in the Merged Outgoing Rotation Group of the CPS for the years 1979 to 1999. We focus on all women between the ages 25 and 50. We extract information on weekly earnings, employment status, education, age, and state of residence. The sample contains nearly 900,000 observations."

However, when I download the data and follow their conditions than I only obtain some 145,000 observations instead of 900,000. My Stata-code is as follows:

use "http://www.nber.org/morg/annual/morg79.dta", clear
forvalues i=80/99 {
    display `i'
    quietly append using "http://www.nber.org/morg/annual/morg`i'.dta"
}

//We extract data on women in their fourth interview month in
//the Merged Outgoing Rotation Group of the CPS
keep if sex == 2 & intmonth == 4

//We focus on all women between the ages 25 and 50.
keep if age > 24 & age < 51 

//We extract information on weekly earnings, employment status,
//education, age, and state of residence.
keep age uearnwk state esr grade92

describe

Does anyone have an idea what's wrong here? I am thankful for any advise.

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    $\begingroup$ I think you want keep if sex == 2 & minsamp == 4. The count would be 876880. $\endgroup$
    – Roberto Ferrer
    Apr 25, 2014 at 23:13
  • $\begingroup$ No chance I could have found this on my own. Thanks, Roberto. $\endgroup$
    – Roberto Liebscher
    Apr 26, 2014 at 0:04
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    $\begingroup$ You also might want to consider something like looping over use age uearnwk state esr grade* sex intmonth age if inrange(age,25,50) & sex==2 & minsamp==4 using "nber.org/morg/annual/morg`i'.dta", clear $\endgroup$
    – dimitriy
    Apr 26, 2014 at 0:06

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