calculating y-o-y growth

[JohnK]

Dear SAS Users,

I have panel sales data as follows for different firms. How can I calculate year-on-year sales growth? I want something like growth=100*dif12(sales)/lag12(sales) but I don't want dif12 to compare values of different firms.

Thanks for any help in advance.

Firm	year	month	sales
1	2002	1
1	2002	2
1	2002	3
1	2002	4
1	2002	5
1	2002	6
1	2002	7
1	2002	8
1	2002	9
1	2002	10
1	2002	11
1	2002	12
1	2003	1
1	2003	2
1	2003	3
…	…
100	2011	12

[art297]

Does the following do what you want?:

data want;

  set have;

  by firm;

  if first.firm then counter=1;

  else counter+1;

  growth=ifn(counter gt 12,100*dif12(sales)/lag12(sales),.);

run;

[Ksharp · Accepted solution]

ArthurT,

Your code would not be able to work, If there are some missing monthes or duplicated monthes. But yours is a fast solution.

data have;
input Firm     year     month     sales ;
date=mdy(month,1,year);
format date yymmdd.;
cards;
1     2002     1     1
1     2002     2     1
1     2002     3     1
1     2002     4     1
1     2002     5     1
1     2002     6     1
1     2002     7     1
1     2002     8     1
1     2002     9     1
1     2002     10     1
1     2002     11     1
1     2002     12     1
1     2003     1     1
1     2003     2     1
1     2003     3    1
;
run;
proc sql;
 create table want as
  select *,((select sales from have where firm=h.firm and date=intnx('month',h.date,-12)) -
            (select sales from have where firm=h.firm and date=intnx('month',h.date,-13)) ) /
            (select sales from have where firm=h.firm and date=intnx('month',h.date,-12)) as growth
   from have as h;
quit;

Ksharp