The fallacy of straight-line projections
On S-curves, fire departments, and the mistake that often clouds our judgment looking both forwards and backwards
An often-cited logical error is the linear projection fallacy, which happens when people assume that the future will look like a straight-line leap forward from the present. Rarely, if ever, is this true. Things change in fits and starts, growth starts out exponentially before leveling out in an S-curve, or some external variable changes the dynamics of what was being forecast.
■ The wise remain alert to the tendency we all have to stumble into this fallacy. But for all our shortcomings looking forward, we are often even worse at looking backwards. It’s difficult to contextualize backwards except in broad brushstrokes, but the effects can be awfully misleading.
■ We paint a historical portrait of Benjamin Franklin that depicts a Founding Father who had all of the big ideas sorted out. And he was, no doubt, an ingenious organizer. But we often lack a sense of scale.
■ Franklin was a citizen working on a level well within reach of us today. Many of his creations of great civic renown were improvements to his beloved city of Philadelphia. He was a major innovating force for the public library (the Library Company of Philadelphia), the fire department (the Union Fire Co.), and the humble city sewer and street-sweeping agency.
■ Philly may have been America’s biggest city at the time, but it wasn’t big by any objective measure today. When it was overtaken by New York City in the 1790 Census, Philadelphia had 28,522 residents -- a completely unremarkable figure, when compared to literally more than a thousand cities of the same size in America today. About half of all Americans live today in places at least as big as Franklin’s Philadelphia.
■ This should tell us that great improvements in municipal living are well within reach. We shouldn’t be daunted by issues of resources, technology, or scale: If Franklin could innovate under 1700s-era limitations (no electric light, for one thing, and an inflation-adjusted GDP per capita of about $2,500), in a town with fewer than 30,000 residents, then very little stands between him and us that can’t be easily overcome with imagination and drive.
