Update needed  

 The results of the EMC collaboration (ration >1 in the low x region, < 1 in the high x region) are no longer latest state of the art.  In the past 30 years many more experiments have been done with considerably higher precision.  The ration per x has turned out to be a wavy curve rather than a linar relation:  at low x ( <0.1) it is less than 1, in intermediate x (approx 0.2) there is a slight overshooting and then it gets negative again. At very high x (close to 1) it gets positive again. See e.g. Fig.2 in http://cerncourier.com/cws/article/cern/53091