SELECT  DV.[Year], 
        SOH.SalesPersonID,
        AverageOrderAmt = SUM(SOH.TotalDue)
FROM    Sales.SalesOrderHeader SOH
CROSS
APPLY   (SELECT DATEPART(yyyy,OrderDate)) DV ([Year])
GROUP   BY 
        DV.[Year], 
        SOH.SalesPersonID
ORDER   BY
        DV.[Year] ;