Posted by Scott Lamb, a resident of the Monta Loma neighborhood, on Mar 6, 2013 at 12:31 pm
Your math is wrong. You said "more than four times [0.8 percent] take such daily treks in the Bay Area." That'd be 3.2%. Neither the quoted number for the San Francisco area (2.06%) nor the San Jose area (1.9%) exceed that. At least one of these numbers (4, 0.8%, 2.06%, 1.9%) is wrong, or you're considering the Bay Area to be something other than San Francisco area + San Jose area. I think you just miscalculated.
Did you *add* 2.06% and 1.9%?!? You can't do that! By the same reasoning, since 100% - 2.06% = 97.94% of residents of the San Francisco area don't have mega commutes and 100 - 1.9% = 98.1% of residents of the San Jose area don't have mega commutes, 97.94% + 98.1% = 196.04% of residents in the combined area don't have mega commutes. Only 100% - 196.04% = -96.04% have mega commutes, by far the least in the nation. Same operation, absurd conclusion. The operation is flawed. The number you apparently calculated, 2.06% + 1.9% is (San Jose megacommuters) / (San Jose residents) + (San Francisco megacommuters) / (San Francisco residents) = 3.96% ...unlike units...which means nothing.
A correct formula would be (San Francisco megacommuters + San Jose megacommuters) / (San Francisco residents + San Jose residents) = (combined megacommuters) / (combined residents). You can probably find the figures for this on the American Community Survey website. Or you can just know that a weighted average must fall between its most extreme components (1.9% and 2.06%), so "more than twice the national average" would be true; "more than three times the national average" would be false; "more than four times the national average" isn't even close.
The Campaign to Correct Math in Journalism starts right here, right now!