Taking up these points in order, we shall inquire first into the causes of the agrarian readjustments of the fourteenth century. A generation after the Black Death, the commutation of villain services and the introduction of the leasehold system had made notable progress. The leasing of the demesne has been attributed to the direct influence of the pestilence, which by reducing the serf population made it impossible to secure enough villain labor to cultivate the lord's land. The substitution of money rents in place of the labor services owed by the villains has been explained on the supposition that the serfs who had survived the pestilence took advantage of the opportunity afforded by their reduction in numbers to free themselves from servile labor and thus improve their social status. The connection between the Black Death and the changes in manorial management which are usually attributed to it could be more convincingly established had not several decades elapsed after the Black Death before these changes became marked. A recent intensive study of the manors of the Bishopric of Winchester during this period confirms the view of those who have protested against assigning to the Black Death the revolutionary importance which is given it by many historians. On these estates the Black Death "produced severe evanescent effects and temporary changes, with a rapid return to the _status quo_ of 1348."[12] The great changes which are usually attributed to the plague of 1348-1350 were under way before 1348, and were not greatly accelerated until 1360, possibly not before 1370, and cannot, therefore, have been due to the Black Death.