Openspace acquisition is a growth management tool. Purchasing openspace prevents houses from being built. This page evaluates the effectiveness of openspace acquisition as a growth management tool. There is information on growth management in Charlestown in the background.

It is possible, using the model presented in the background section of this portion of the site, to evaluate the effectiveness of different scoring systems in controlling growth. The graphs on the right show the percentage of houses prevented from being built, as a function of the amount of money spent purchasing openspace using assessed value.

The top graph uses the scoring system from the web survey, the bottom graph uses the scoring system from the planning and conservation commissions. The differences between the two scoring systems are minimal, as shown by the third graph.

This graph shows the percentage difference at any given point in the acquisition program between the two scoring systems. The largest difference is only 5%, and at most levels of openspace acquisition the difference is less then 2%.

This shows that there is the difference between the potential growth management of the two systems is small. This is to be expected because the number of points that were appropriate to growth management in each scoring system are very close.

It is apparent in both graphs that the more then half of the units are prevented in the first 10 million dollars that will be spent on acquisition. This means that first parcels that are purchased have a high number of potential units for the amount of money that they will cost to purchase the parcel.

This is partially due to scoring system, which ranks parcels with a large number of potential units and low costs higher then those with high costs and a small number of potential units. The graph on the right shows the cost per unit prevented as a function of the number of units prevented from being built. This shows that the most efficient parcels are being purchased first and is evidence that the scoring system is working.

The graph on the right shows the number of potential units in each parcel as a function of the amount of money spent purchasing openspace. This graph shows that parcels with more potential units tend to be purchased before parcels with fewer units.