With the sharing of these data, we have to balance the (potentially competing) needs to make the data accessible, consistent across states, and flexible. States are not consistent in how they can share these data, so we’re not able to make the datasets completely apples-to-apples.
We can sometimes share part of the vehicle identification number (VIN) for an individual registration. In other cases, the state DMV interprets the VINs before sharing the data.
For the EV Hub, we’ll only post the first eight to eleven digits of the VIN to avoid sharing anything that could be considered personably identifiable. The VIN is the most reliable way to make sure you’re interpreting the vehicle registration correctly: is it a conventional version of a vehicle or the electric version? So, we give you part of the VIN data directly along with our VIN decoder, which is a simple table of plug-in electric vehicles available in the United States.
Our target audience for the EV Hub are professionals in public policy so we don’t have personally identifiable information like the address of a vehicle. Instead, we aggregate the total number of vehicles by make and model to the ZIP code level.
Vehicle registration datasets are typically snapshots in time of the vehicles “on the road” in a state. Thus, we need multiple snapshots to piece together changes in the market over time. We also need the complete VIN in order to determine when the vehicle first entered the state’s market (new or imported from elsewhere). That is, the first time it appears in the database, we consider it an “original” registration and subsequent occurrences of that VIN are treated as a “renewal” registration. If we don’t have the full VIN, then we can’t reliably track metrics like original or renewal registrations unless the DMV shares that information directly.
Regarding time series analyses, we’ll ideally get snapshots of the vehicle registration database frequently enough to be able to understand how the market has changed over time. With each state vehicle registration data file, we include the DMV snapshot date and a unique identifier to make it easier to interpret the data.
Some states aren’t able to share these snapshots frequently or they don’t share the vehicle’s registration date. For states where we don’t know the vehicle registration date, we’ll assign the registration date to the day the snapshot was taken or delivered to us.