I assumed the base amount for the last 10 years. There are obvious factors at each airport that contributed to their respective growth, but for simplicity, I assumed Bay Area growth continued on the same trajectory as their post 2008 numbers have shown. The Bay Area is the 3rd largest O&D market in the country so demand will always be here. Growth may slip a little, but without running or viewing a full forecast, I used the last 10 years growth pattern as a baseline. There could be a significant economic downturn again or another 9/11 but those are difficult to predict when and how much impact they would have. If you have a better model or idea of how to estimate the growth rate of the Bay Area for the next 15 years I would love to see it!
Well the FAA provides forecasts, for one, but I think the mental exercise you're trying to go through is flawed, at least for a constrained environment. If slot controls are enacted at SFO, net growth for the region over the long term will slow down, period. Fares will go up and demand will not increase at as fast of rates. There will continue to be some aircraft upgauging. Some connecting traffic will be replaced by O&D traffic.
Again, if you have a better growth rate to go off of, by all means present it as I would love to see it. But if you want to poke holes without contributing any ideas how to improve this forecast model then that's not really helpful now is it? Forecasting is an art not a science. I am factoring a conversation growth rate. SFO is going from 50m to 60m in 3 years. SFO has stated with their runway configuration their max capacity is 82 million. Growing an average of 2m a year of the next 12 years until the 2030 is definitely less than what SFO has been doing. If OAK and SJC even just keep posting 1m annual growth rates each over the next 12 years (at the same pace they have been growing recently) and SFO slows growth by 40% these airport limits by 2030 will still be reached. This is an even slower prediction than the Bay Area Economic Council's 2016 forecast for Bay Area growth specifically the air service growth. We can see next year when they release the 2019 edition if anything changes but I would doubt it will be slower. I was at a conference in March where the CFO of SFO spoke and said SFO will reach maximum terminal build out around 2026-2030 if the rest of there long term construction funding is approved. All this lines up with my assumed conservative growth rates.
Sona forecasts are about assumptions.
If you assume unconstrained facilities, no increase in input costs, no real increase in fares, continued Bay Area outperformance economically, well that long-term rate is probably 3%.
If you assume constrained facilities, increases in input costs, increases in fares (themselves dependent upon constrained facilities), and a potential tech slowdown, well the long-term rate might be 1%.
You assume whatever it is you want to assume. But your methodology is flawed because you are not factoring in potential facility constraints, i.e., you say because the Bay Area airports have grown collectively by 5m p.a. for a recent period, they have to
grow at similar rates in the future, even if SFO goes under slot contro
l. That logic is very transparently flawed