Cost per watt of solar panels

As the cost of solar panels has plummeted, deaths from ATV and off-highway vehicle accidents have also declined, a correlation that suggests either that renewable energy makes people safer drivers or that two trends declining simultaneously need nothing more than a shared calendar to produce an impressive number. The coefficient is 0.841 across seventeen years, during which both metrics fell—one because of Chinese manufacturing, the other because of helmet laws—and the chart treated both reductions as evidence of the same phenomenon.

Solar panel costs fell from about $4.00 per watt to under $0.30 between 2005 and 2021, driven by manufacturing scale and technology improvements. ATV deaths declined from about 870 to under 600 per year, driven by state-level helmet mandates, age restrictions, and improved vehicle safety standards. Both trends are downward-moving curves during the same period, which guarantees a positive correlation (both going down = positive r). The mechanisms are entirely separate: one is a manufacturing cost story, the other is a recreational safety story. They share a direction and a decade, nothing more.

Seventeen years of solar costs and ATV deaths both declining is a coincidence so clean it could be framed: two things getting better at the same time, for different reasons, in a world that occasionally produces good news from multiple directions simultaneously. The panels get cheaper, the rides get safer, and the correlation is simply progress happening in parallel.