The dummies for Florida and California are the state for each work duration, and not
necessarily the state at the time of interview. Before 1993 dummy variable is for all the years prior
to 1993 when the majority of IRCA legalization was granted, and After 2001 is the years
post-September 11, 2001 event.
Duration or farm work spells is a variable created from the work grid in the questionnaire.
It is the difference between the ending dates and starting dates for each “farm work” spell, and
only includes the completed spells (all spells completed at the time of interview).
Ordered Probit Model for Legal Status
Here we estimate the ordered probit model for legal status for foreign-born farm workers
using NAWS data. Table 1 shows estimates for parameters and asymptotic standard errors (given
in the parentheses) using 30912 observations of foreign-born farm workers. Using a 0.05
significance criterion, we find that all coefficients except education squared are statistically
significant.
The third column of Table 1 shows the marginal effect of each variable on the probability
of a worker being legal. The probability of worker i being legal is given by
Pr ob( J** > μ0) = 1 - Φ(μ0 - xi 'α). Then the marginal effect of variable k evaluated at the mean is
φ(μ0 - x'α)αk for the continuous variables6 and Φ(μ0 - x'_k α-k ) - Φ(μ0 - x'_k α-k - αk ) for the
dummy variables, where x'-k and α-k are variables and coefficients excluding k. Females,
married, workers with higher English speaking ability, non-black, white, non-hispanic are
statistically significantly more likely to have more advantageous legal status all else being the
6 Marginal effect for variables with squared term is given by φ(μ0 - x 'α)(αk + 2αk sqx ) where αk sq is
coefficient for the squared variable. Also, we treated English speaking ability as a continuous variable.
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