Input-output analysis, long used by national planners, is being used by economists in California Cooperative Extension to help local governments develop economic information to aid in making resource planning decisions. As the name suggests, input-output analysis involves tracing the purchases (input) and production (output) of different sectors in an economy. Data are gathered on actual production and consumption relationships among the sectors. With this knowledge, an economic model of a selected area is created so that the effect of changes in any sector's production on all the othersector's can be measured. These models can and have been created on a national, state, regional, county and city basis.