What is Diversity Factor in Electrical Loads

Dear Friends, I need to clear exactly wht is diversity factor and y we do that. I Have a example aboutthe diversity factor which i need to explain with one example. I have total load connected for motors is about 745kW and running load is 559kW .then diversity factor is 559/745 = 0.75 is the diversity factor. please can any body tell me what does this mean. I have heard about that diversity effect to cost of power generated at loads and it also says that if diversity is greater than 1 it means low cost . I really want to know after getting 0.75 as the diversity what does this mean. Please i know CR4 is the place where i m not shy to ask but i need to clarify. Thanks sam