This paper examines two due-date setting problems first studied by Wein (19
91). The first problem seeks to minimize the average due-date lead time (du
e-date minus arrival date) of jobs subject to a constraint on the fraction
of tardy jobs (Problem I) while the second uses the same objective subject
to a constraint on average job tardiness (Problem II). We show that under v
ery general conditions, Problem I leads to unethical practice (i,e., quote
lead times for which there is no hope to achieve when the system is highly
congested) while Problem II results in policies that quote lead times that
are monotonically increasing with the congestion level. Furthermore, we pro
ve that Problem II is equivalent to a policy that is widely used and is eas
y to compute. This policy quotes lead times that guarantee the same service
ability level (the fraction of tardy jobs) to all jobs.