st: Confusing collinearity error message from -ice-

[Mike Lacy <Michael.Lacy@colostate.edu>]

I'm using -ice- in order to take advantage of its -interval() 
command, so as to be able to prevent nonnegative variables (e.g., 
area of land owned) from having negative values imputed.  I keep 
getting a collinearity error message whenever I try to run it while 
including the variables specifying the lower and upper limits, as 
-interval- requires.  I'm using -ice- 1.7.3. Here's what I have for 
code and relevant output:

// Create lower and upper limits variables for -interval- option
. gen llagsale = 0
. gen ulagsale = 500 // max observed
. gen llacres = 0
. gen ulacres = 1300  // max observed
. gen llincpert = 0
. gen ulincpert = 100 // max observed
. //
. ice years female workoff  ///
>   agsales1000 acres100 incpert  llagsale ulagsale  llacres 
ulacres  llincpert ulincpert  ///
>   spiritualconnect preservation econdependence,     m(10) clear  ///
>   interval(agsales1000:llagsale ulagsale, acres100:llacres 
ulacres, incpert:llincpert ulincpert)

   ... snip, snip

   Variable | Command | Prediction equation
------------+---------+-------------------------------------------------------
   .snip, snip
            |         | spiritualconnect preservation econdependence
    workoff | logit   | years female agsales1000 acres100 incpert

snip, snip
// Error messages start here

Imputing
[Note: in regression for workoff, dropping agsales1000
 acres100 incpert due to collinearity]

[Note: in regression for years, dropping agsales1000 acres100 incpert
due to collinearity]

etc.
============================

What confuses me about the collinearity reports is that the three 
variables reported as offending are only modestly correlated 
(0.2-0.3).  The problem seems to come from the limit variables, since
when I omit them and omit the -interval- option, I don't get the 
collinearity errors. (The imputed values, though, are way out of 
range.)  So, I would like to use the -interval- option.  Any thoughts 
here about what's going on?

Regards,


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