<Tr> <Td> 2003 </Td> <Td> Life for Rent </Td> <Td> Dido </Td> <Td> United Kingdom </Td> <Td> 12.0 </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td> Under My Skin </Td> <Td> Avril Lavigne </Td> <Td> Canada </Td> <Td> 12.0 </Td> <Td> </Td> </Tr> <Tr> <Td> 2003 </Td> <Td> Get Rich or Die Tryin' </Td> <Td> 50 Cent </Td> <Td> United States </Td> <Td> 12.0 </Td> <Td> </Td> </Tr> <Tr> <Td> 2000 </Td> <Td> Music </Td> <Td> Madonna </Td> <Td> United States </Td> <Td> 11.0 </Td> <Td> </Td> </Tr>

Who is the biggest selling artist of the 21st century