In contrast, the incidence proportion can be calculated as 16 â 2,100 = 7.6 cases per 1,000 population during the four-year period, or an average of 1.9 cases per 1,000 per year (7.6 divided by 4 years).
The Costs. Minimum Cost: Approximately $.50 per square foot. Maximum Cost: Approximately $2 per square foot. The size of roofs vary immensely from a standard, urban roof measuring about 800-square-feet to suburban roofs, which often range above 1,500-square-feet.aximum Cost: Approximately $2 per square foot. The size of roofs vary immensely from a standard, urban roof measuring about 800-square-feet to suburban roofs, which often range above 1,500-square-feet.
In terms of a ballpark figure, though, Michael Allen, owner of Above It All Roofing in Irvine, California, says the average cost of a new roof runs as low as $5,000 for a basic asphalt shingle roof â the most commonly used roofing material in America â to $25,000 and up for higher-end roof types.