Estimating Population of Mercury
Convenience Light Switches

Model Overview
The NVMSRP model estimates the number of mercury switches in end of life vehicles over time by state. An overview of the model with switch retirement estimates by state can be found by clicking the link on the left. The complete model can be accessed by clicking the link below the overview.

Reference/Source Data
To review references and source data for the estimate, please click on link.

How the Model Works
1) The population of vehicles which may have mercury switches still on the road as of July 1, 2006 is determined from R. L. Polk & Co. (herafter referred to as “Polk”) registration data.*

2) The adjusted mercury switch per vehicle data from Michigan Switch Study and population from step #1 is used to estimate the number of mercury switches in vehicles as of July 1, 2006.

3) 1997 to 2006 Polk data is then used to calculate an average scrappage rate for this period. The 1997 to 2006 average scrappage rate is then blended with the Oakridge model scrappage rates. The resulting scrappage rate is used to calculate the rate at which the switches from step #2 retire.

4) The estimated number of switches available for collection is then calculated by subtracting inaccessible switches due to vehicle damage, end of life vehicle exports, and lost or stolen vehicles which do not enter the recycling stream from the numbers generated in step #3.

Mercury retirement rates are estimated to accurate within +/- 10% through 2017. Post 2017 estimates have greater uncertainty.

Model Evaluation
In 2012, the model was evaluated by the NVMSRP data management group for potential revision. Based on the evaluation, the conclusion of the group was that the model understates the number of switches available for collection but that revising the model would not result in significant changes to capture rate calculations and was therefore unnecessary. The NVMSRP will continue the use the current version of the model as the basis for determining the number of switches available for collection. To view the model evaluation, please click on the link.

* The analyses and results expressed herein are those of the NVMSRP Measurement Committee and do not reflect conclusions derived by R. L. Polk & Co.