Why does some key figures differ from one annual report to another

I´ve started to read some annual reports lately and inserted some into my excel sheet to calculate some key figures, but saw that column with "Total assets" differ than reads in the last years report.

              2007        2006
TOTAL ASSETS  5,551,614   3,742,338

and another year

              2008         2007
TOTAL ASSETS  2,781,656    5,262,960

2008 Annual Report – ABG Sundal Collier Holding ASA

2007 Annual Report – ABG Sundal Collier Holding ASA

What needs to be taken for the calculation of the various numbers?