4. Staff costs

Staff costs of the Group were as follows:

2007/08
$m
2006/07
$m
2005/06
$m
Wages and salaries 635.7 619.8 557.8
Social security costs 54.5 51.9 45.7
Pension costs 11.4 10.9 9.4
Share-based payment expense 0.4 6.7 8.1
Total staff costs 702.0 689.3 621.0