Recently, about 40,000 environmental activists recently descended on Lower Manhattan for what they deemed a global climate strike. Many of the protesters marched with a specific goal in mind: to convince Comptroller Thomas DiNapoli to purge $13 billion in fossil fuel investments from New York State’s $210 billion pension fund.

These protesters aren’t alone. All across the country, environmentalists are urging public pension managers to sell their fossil fuel assets. If pension managers were to embrace divestment, the thinking goes, oil and gas companies’ share prices would plummet. Firms would struggle to raise capital in the future. Thus, they’d shelve expansion plans and keep more fossil fuels in the ground.