Proponents of electric vehicles — EVs — in large measure due to the fascination and hype associated with Tesla, describe a future transportation system that borders on revolutionary. For example, Bloomberg New Energy Finance recently published a report — “Electric Vehicles — It’s Not Just About the Car” — that forecasts radical changes in our automotive transportation system by 2040.

While it is instructive to see how the commercialization of electric vehicles would change our transportation system, Bloomberg builds its narrative using the forecaster’s best friend, rosy scenario.

Bloomberg forecasts that by 2040 global EV sales will be 35 percent to 47 percent of new vehicle sales. That estimate is predicated on a rapid decline in the cost of batteries.

Long-range forecasts are always risky because the farther out in time they go, the more that unknowns affect them. While declining battery cost is essential, range, durability, government policy, power generation capacity and advances in engine technology are just as important.

Rather than looking at the global market for light-duty vehicles to test the reasonableness of the Bloomberg forecast, the test can be the U.S. market.

According to the Energy Information Administration’s 2016 Annual Outlook, there are 242 million light-duty vehicles on the road today. By 2040, that number grows to 280 million, but only 6.8 million are EVs.

The growth that takes place in electric vehicles over the next 25 years comes mainly from conventional hybrids and plug-in hybrids, which combined will still represent less than 10 percent of the light-duty fleet. Sales of plug-ins and EVs in 2040 are forecast to be about 950,000. Light-duty vehicles sales are forecast to be about 18 million. Thirty-five percent of 18 million is 6.3 million, which is almost seven times greater than EIA’s forecast for both plug-in and EV combined. If Bloomberg is assuming that sales of EVs are the greatest outside of the United States, it is being wildly unrealistic.

If battery costs are the driver, they have to get much lower than today’s $600/Kwh. While that is a substantial reduction from the $1,000 in 2013, most analysts conclude that to be competitive those costs have to get at least to the $250 target set by the U.S. Advanced Battery Consortium.

Lithium-ion batteries represent the current state of the art and that is the battery that Tesla’s mega factory will be producing on a large scale. Although mass production helps lower the cost of EV battery packs, it does nothing to improve safety, a major problem, or endurance.

In 2015, MIT’s Technology Review published an article on why there haven’t been battery breakthroughs. It made the point, “While countless breakthroughs have been announced over the last decade, time and again these advances have failed to translate into commercial batteries with anything like the promised improvements in cost and energy storage.”

According to the article, the reason is simple, “One difficult thing about developing better batteries is that the technology is still poorly understood.”

Chalk a battery breakthrough as a major unknown.

Rather than wither away, as Bloomberg suggests, the market for internal combustion engine vehicles remains robust and there is every reason to believe that it will remain that way for the foreseeable future. When EVs become commercially viable without large purchase subsidies and without taxpayer funding for charging stations, the transition will be gradual and the market will adjust unless the heavy hand of government gets in the way.

The Bloomberg forecast makes interesting reading but to paraphrase Mark Twain, the rumors of the demise of the internal combustion engine and the industries built to support it are greatly exaggerated. It also demonstrates that if you know what you want a forecast to show, rosy scenario can take you there. Like the horizon, the end of the automobile age as we know it today recedes as we approach it.