average array formulae return different results

Hi,

Please can you help me understand why this formula is not working i.e. it is returning zero?

=AVERAGE(IF(AND(Pension!$F$5:$F$52<=20000,Pension!$F$5:$F$52<=20000),Pension!$L$5:$L$52)) entered with ctrl+shift+enter

This version without the AND statement works fine:

=AVERAGE(IF(Pension!$F$5:$F$52<=20000,Pension!$L$5:$L$52)) entered with ctrl+shift+enter

Thanks

Andrew