How to get the sum of one kind of agent's property?

[Young Jay Cheung]

I have built a economic model for supply and demand.
I
 have two kinds of agendts which are Consumer agent and Enterprise agent.

The Enterprise agent will decide the production according to the total consumption of Consumers. The Consumer agent have the "consumption" property. In the chart displaying, it is  easy to get the sum of consumption of Consumer agents by choosing the aggregate mapping model. But the data of total consumptio only display in the charts. Enterprise can not get the value of total consumption during the simulation.

Anybody can told me how to get the sum of Consumption property?

Thanks in advance.

Jay