The Wisconsin Longitudinal Study uses negative integers starting with -1 to
indicate missing values.  
 
For all numeric variables in the WLS, the Stata program statawls will convert 
these missing values to Stata missing values.  It will also change the value 
labels so that they remain correct.  Additionally, the command can also be 
used to change all variable names from uppercase to lowercase (or vice versa).
 
After downloading the WLS dataset, you can run statawls once, save the 
resulting dataset, and work from that for all your analyses. 
 
If you know how to install and run Stata ado and help files, you can follow the 
same practices to install and run statawls.  Otherwise, statawls.ado is an 
add-on Stata command, and like all add-on commands, it needs to be installed in 
a location where Stata will find it.  If you type -sysdir-, you can see what 
directories Stata searches for .ado files.  If you have write privileges to the 
directory listed as PLUS or PERSONAL, we recommend installing it there.  Just 
copy the files into that directory and they should work.
 
Stata will also search the working directory for .ado files.  You can see what 
directory Stata has set as the working directory by typing "cd".  If you type 
"cd" and a path, you can change the working directory to whatever you want.
 
After statawls.ado has been put in the PLUS, PERSONAL, or working directory, 
all you need to do is type:
 
    statawls, lower
 
If you want statawls to change all the missing values and change variable 
names from uppercase to lowercase.  Leave off the ", lower" if you want to 
leave variable names as is.  If they are already lowercase and you want to 
make them uppercase, you can specify ", upper" instead.
 
If the .hlp file is installed in either the PLUS, PERSONAL, or working 
directory, you can get more information on statawls by typing "help statawls"