I have got two tables
table 1 has data for year 2000 as follows
Company ID Units_jan Units_feb...... ......Units_Dec
ABX 12 3 5 .............45
34 5 454 354354
............... .
table 2 has data for year 2001 as follows
Company ID Units_jan Units_feb...... ......Units_Dec
AwX 12 ...