I did not see a SQL response to this post so here is a possible SQL solution

data tsts;

input country : $3. year : 6. density :6.2;

cards; USA 1952 1.0 USA 1953 1.1 USA 1954 1.5 USA 1955 2.1 USA 1956 2.6 USA 1957 3.0 UK 1952 0.8 UK 1953 1.1 UK 1954 1.5 UK 1955 1.3 UK 1956 1.1 UK 1957 2.0 ;;; run;

proc sql;

select a.*, b.density as dennew

from tsts a left join tsts b

on b.year eq 1955 and b.country eq a.country ;

quit;

run;

output from sql

The SAS System

COUNTRY YEAR DENSITY DENNEW

UK 1955 1.3 1.3 UK 1953 1.1 1.3 UK 1957 2 1.3 UK 1956 1.1 1.3 UK 1954 1.5 1.3 UK 1952 0.8 1.3 USA 1957 3 2.1 USA 1954 1.5 2.1 USA 1956 2.6 2.1 USA 1955 2.1 2.1 USA 1953 1.1 2.1 USA 1952 1 2.1

Roger J DeAngelis CompuCraft Inc XLR82SAS@aol.com ( Accelerate to SAS ) http://members.aol.com/xlr82sas/utl.html