What are the main reasons in the inventory shrinkage, especially in inventory with 10000+ varieties?

Hello There,,   From my experiance in Retail Management and Inventory Control here in the USA and I've been doing this for quite a while ,, the reason for your Inventory Shrinkage is almost always  INTERNAL THEFT ,,, It counts for over75% of any Profit Center,,, So my Friend alway keep an eye on the inside more than the outside..
I hope I was of help to your problem,, Warmest Regards, Fawaz Haddadin Chicago  

common reason why shrinkage is beacause of internal theft.

1-           Poor communication with client, training the staff and checking their weakness  

2-           Delay in delivery, must be Commitment with the deadline

3-           Losing customers to competitors with better offerings, study the markets and our products

 

Thanks Fawas...
It is true that the main reason for the shrinkage is internal theft... 
Can you list out the others...