12,560 observations, status 2 (permanent resident) workers have 30,240 observations, and status 3
(citizen) workers have 18,307 observations. Based on asymptotic standard errors using a 0.05
significance criterion, the coefficients on the selectivity variable, λ, are all significant except for
citizen workers. That is, using ordinary least squares without correcting for selectivity would lead
to bias in all equations except for citizen workers. Actually, the selection bias correction term is
set to zero for majority of citizen workers, because they are native born. So, the selection bias does
not have a significant effect for this equation as it does for the other legal status equations.
Many variables have a statistically significant effect on duration in a common direction
for all equations. Regardless of the legal status, workers in tasks requiring higher skill,
non-seasonal workers, workers without free housing from employers, workers in California,
workers in Florida, and workers interviewed after 2001 are statistically significantly more likely
to have a longer duration farm job. Most of the signs of these coefficients are reasonable, except
for the availability of free housing offered by the employer, which we expected to have a positive
effect on duration. This may be because workers offered free housing are often migratory,
seasonal workers with low skill and whose length of contract is generally short.
An interesting result is for English speaking ability. For unauthorized workers, higher
English speaking ability is more likely to lengthen the duration in farm work. However, English
speaking ability tends to shorten the duration in farm work for authorized and permanent resident
workers. That is, legal workers leave agricultural work earlier as their English speaking ability
improves, all else being the same. This variable does not have a significant effect on duration of
citizen workers most of whom (77 percent) can speak English well, so that the variable has little
variation.
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