Description of Implan methodology

Doug, I am writing up the results that you helped me with a few months ago (thanks again!). I am looking for some general discussion (very general) about how IMPLAN calculates the impacts of events. In the past, we've used the following description. Is this still accurate with Version 3.0? Or, can you point me to some general descriptive text so I can revise it? Thanks. [i]IMPLAN is based on an input-output accounting of commodity flows within an economy from producers to intermediate and final consumers. The model establishes a matrix of supply chain relationships between industries and also between households and the producers of household goods and services. Assumptions about the portion of inputs or supplies for a given industry likely to be met by local suppliers, and the portion supplied from outside the region or study area are derived internally within the model using data on the industrial structure of the region. The output or result of the model is driven by tracking how changes in purchases for final use (final demand) filter through the supply chain. Industries that produce goods and services for final demand or consumption must purchase inputs from other producers, which in turn, purchase goods and services. The model tracks these relationships through the economy to the point where leakages from the region stop the cycle. This allows the user to identify how a change in demand for one industry will affect a list of over 500 other industry sectors. The projected response of an economy to a change in final demand can be viewed in terms of economic output, employment, or income. Data sets are available for each county and state, so the model can be tailored to the specific economic conditions of the region being analyzed. This analysis utilizes the data set for ____ County. The City is, of course, part of a larger regional economy and impacts will likewise extend throughout the region. However, to be conservative, only employment impacts occurring within the county have been included.[/i]