How much does the data rate in LTE vary from center of the cell to the cell edge?

LTE uses adaptive modulation. Where at the center of the cell the channel specs are great so a high data rate modulation can be used (ex.64 QAM) . But on the cell edge the channel specs is not that reliable to use a high data rate modulation so we use a lower order of mudulation (ex. QPSK)  To ensure the correct detection of symbols at the receiver.