Discontinuities

In October 1908 Ford Motor Company produced 11 Model Ts. In 1909, Ford produced 10,000. In 1912, 68,000. Production growth was mostly driven by growth in the number of workers and in factory square footage. There were also incremental innovations in the production methods such as numbering the discreet steps (84) from start to finish and training workers to complete only one.

In 1913, Ford produced 170,000 Model Ts, cutting the production time from 12 hours to 93 minutes. That's a ~250% year-over-year growth rate while reducing production time by 87%.

This is an example of a discontinuity. The rate of production (Model Ts per year) from 1908-1912 does not continue in 1913.

This is how we might normally visualize Model T production over time.

Here's how it would look including the discontinuity:

This version helps us begin to understand better. It prompts the question: what happened in 1913?

Charts and graphs tell stories. They also hide stories. For the past decade at Teach For America, I've studied the stories that the graphs charting the rise and fall of trends and outcomes in education tell us. Over time, I've also grown curious what they hide and when they might be masking discontinuities. I look forward to sharing some of what I've found in the coming posts.  

The 1913 discontinuity in Ford's Model T production? The assembly line.