The SPARSE Option The SPARSE option in PROC FREQ is not properly named. It is neither meager nor thin in its ability. It is a very powerful option in the table statement. Simply stated, the SPARSE option provides “all possible combinations of levels of the variables in the table, even when some combination levels do not occur in the data.”1 This is a huge help when trying to zero-fill a data set. Although current versions of SAS® now contain the new PRELOADFMT option for TABULATE and REPORT, for some types of reports, this new option will not work.
See the article by Chris Moriak