This works for your sample data, but is your sample data representative of you actual data. data stale;    input DATE PRICE;    d = dif(price);    cards; 1995     3 1996     4 1997     2 1998     2 1999     2 2000     3 2001     4 2002     5 2003     2 2004     2 2005     2 2006     2 ;;;;    run; data stale2;    do _n_ = 1 by 1 until(eof1);       set stale end=eof1;       by d notsorted;       if first.d and d eq 0 then _obs_=_n_;       end;    do _n_ = 1 by 1 until(eof2);       set stale end=eof2;       if _n_ lt _obs_ then output;       end;    stop;    run;    ... View more