What is diversity factor in electrical installation?

When you are determining the electrical load of certain appliances, such as a stove (range), it's unnecessary to add together ALL the individual heating loads (oven, rings, etc.) because, under most circumstances, they are rarely operated altogether at the same time. For example, the IEE Regulations (for the UK) specify that, when determining the total load for a 'cooking appliance', the calculated load current should be 10 A of the overall rated current, plus 50% of the rated current, plus 5 A if the appliance has a socket outlet incorporated.