Possible problems: Data sets not sorted
If you tried to merge the original data sets (which were ordered SUBJ= 1, 7, 9, 5, 8) the following appears in the log.

Data Survey12;
     Merge GenYear HtWt;
     BY Subj;
ERROR: BY variables are not properly sorted on data set WORK.GENYEAR.
SUBJ=9 GENDER=M YEAR=93 HEIGHT=66 WEIGHT=120 FIRST.SUBJ=1 LAST.SUBJ=1 _ERROR_=1 _N_=3
NOTE: The SAS System stopped processing this step because of errors.
WARNING: The data set WORK.SURVEY12 may be incomplete.
When this step was stopped there were 2 observations and 5 variables.
WARNING: Data set WORK.SURVEY12 was not replaced because this step was stopped.