Since the situation described can be viewed as a matter of interval censoring, UCLA's  Institute for Digital Research and Education statistics resources suggest using PROC LIFEREG. http://stats.idre.ucla.edu/sas/dae/interval-regression/ The original suggestion can be found on page 145-146 of one of that article's citations: Long, J. S. 1997. Regression Models for Categorical and Limited Dependent Variables. Thousand Oaks, CA: Sage Publications.   ... View more

Actually, you might want to use DISCRETEORDER=UNFORMATTED instead, since you said your underlying data is in numeric order.   Thanks! Dan ... View more