What to count when counting e-waste?
Which data category to use to count e-waste is a complex issue. I've written about it in depth in a recent article, which you can access for free. See the "Methods" section of:
Lepawsky, J. (2015), The changing geography of global trade in electronic discards: time to rethink the e-waste problem. The Geographical Journal, 181: 147–159. doi: 10.1111/geoj.12077
http://onlinelibrary.wiley.com/doi/10.1111/geoj.12077/full
The politics of documenting e-waste flows is also something I address in some detail here:
http://discardstudies.com/2016/01/04/trading-on-distortion/