Why are your population estimates based on one number and not a range?

We recognize that there is a range of future population estimates; however for planning purposes we have to arrive at a single number.  Based on the current population and assumptions for fertility rates, death rates and future jobs (which affects job seekers moving to the Bay Area), the Plan Bay Area estimate represents what we believe is the most likely future population. To ensure the forecast is as accurate as possible, it will be updated every four years.