California is the most populous state in the US, and has long been considered the most progressive. It has always led the nation in plug-in vehicle sales. But by how much?

According to the California Plug-In Electric Vehicle Collaborative (via Green Car Reports), 52 percent of the plug-ins sold in the US in June went to Californians – 7,161 out of a total of 13,772.

Since the dawn of the EV era in December 2010, 46 percent of US plug-in sales have taken place in California.

The Golden State’s electrical eminence surely has something to do with its residents’ famous green sensibilities and interest in new technology, but the main reason is that the state government has been aggressive about pushing plug-ins.

The California Air Resources Board’s Zero Emission Vehicle (ZEV) mandate has been one of the main drivers of the US EV industry, forcing automakers to produce plug-in vehicles. Cash purchase incentives and other perks, including the coveted green sticker that gives access to priority lanes on the hated freeways, induce consumers to buy.

An arcane rule called the “travel provision” means that cars sold in California count toward quotas in 10 other states that nominally also follow the ZEV regulations. Automakers are lobbying to extend the travel provision indefinitely. If their efforts succeed, plug-in sales will likely continue to be centered in California.

Source: Green Car Reports