About 2 million electric vehicles were sold worldwide in 2018, a whopping 57 percent increase over 2017, according to consulting firm Research and Markets. Some 69 percent of those were battery electric vehicles (BEVs) and 31 percent were plug-in hybrid electric vehicles (PHEVs).

A profound lesson of technological history is that a mechanical thing's purpose and function (i.e., how it achieves this purpose) may diverge over time.