A decade and change ago, as the world woke up to the catastrophe of climate change, campus activists were looking for ways to heal the environment at scale. They landed on an unusual one: the free market. Climate change is the world’s biggest unpriced externality, in that neither the producers nor the consumers of fossil fuels pay for the damage they cause to the environment. Gas is too cheap; ultimately, every living thing on the planet bears the cost. Perhaps activists could get the market to price that externality in by nudging investors to divest.

Students at dozens of universities, galvanized by the nonprofit 350.org, began protesting at academic-leadership and investment offices, asking for endowments to quit holding shares in fossil-fuel companies. The students picketed. They marched. They conducted sit-ins. They held votes. “You do not want your institution to be on the wrong side of this issue,” Stephen Mulkey, the president of Maine’s Unity College, the first to divest using 350.org’s guidelines, told Inside Climate News in 2012. “We realized that investing in fossil fuels was an unethical position.”

Still, the demands sounded symbolic at best, the movement brimming with idealism and energy but to what end? Companies like Chevron and ExxonMobil are profitable because of the world’s unslakable demand for gas; folks dumping their stocks would not change that. Such firms would “find other willing buyers” for the shares, Drew Faust, Harvard’s then-president, argued in response to students’ divestment campaign in 2013. And Harvard, she noted, used no small amount of light sweet crude itself.

But divestment had worked in other contexts: helping to end apartheid in South Africa, for instance. And the financial argument was, in theory, sound. Divestment can reduce a company’s value: Some folks sell their stock, others refuse to buy, the share price falls if there aren’t enough other, interested investors to step in. More important, it makes corporate growth more expensive. Exploration, mining, extraction, shipping—these are all extremely costly for energy firms. If such firms have less cash on hand and a harder time raising it, projects might not pencil out, energy prices might go up, and their profit margins might fall.

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By 2018, less than a decade since the climate divestment movement picked up in the United States, more than 1,000 institutional investors with $6.2 trillion in assets under management had committed to divestment, the firm Arabella Advisors has estimated; some of today’s tallies are several times higher. The list of entities quitting fossil-fuel investment now includes several large pension funds, the country of Ireland, the Ford and Rockefeller foundations, and dozens of private colleges and universities. In 2021, Harvard (under new management) divested. In July, Seattle University did too. Last month, New York University, despite its deep ties with Wall Street, agreed to do so as well.  

Has it worked? On the margin perhaps. Some analyses find that the movement is still too small to have any effect. But one broad analysis of lending to oil-and-gas firms in 33 countries from 2000 to 2015 found that divestment was “associated with lower capital flows,” an effect “enhanced in more stringent environmental policy regimes and diminished in countries which heavily subsidize fossil fuels.”

But the single most important effect of divestment isn’t about the money at all, but something stranger and more diffuse: It takes away the “social license” of the fossil-fuel industry, as the movement’s leader, Bill McKibben, puts it. It makes extractive companies seem socially irresponsible and unworthy of public investment. It makes people think twice about working for such firms. It pushes all companies to acknowledge the environment, and to understand that being a major emitter is a bad business practice. It helps pressure corporate financiers to take climate seriously, something that really will keep the planet livable.

To be clear: A single person selling their Exxon stock is not going to change the trajectory of the climate crisis. A few families committing their 401(k) money to green funds is not going to hasten the world’s transition to renewable energy.

But McKibben is right. Symbolism matters. And if you are worried enough about the climate to want to take personal action, moving your money to green funds is one of the easiest ways to do it—one that takes perhaps five minutes, one time, plus a bit of emailing once a year. Contrast that with quitting meat, giving up your car, or stopping air travel.

If you like to pick your own stocks, the choice is simple: Either divest, or invest with intention. Just don’t buy stocks from major emitters, including coal, oil, and gas companies. Or buy the stocks of brown companies that really are trying to go green, rather than their less-green rivals. Tell these companies at shareholder meetings that you want them to commit to environmental standards. The economists Alex Edmans, of London Business School; Doron Levit, of the University of Washington; and Jan Schneemeier, of Indiana University, call this strategy “tilting.” “Divestment is most effective at starving a company of capital and hindering expansion, but tilting is more powerful” at getting a company to lower its emissions, the economists have found.   

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Jacquelyn Pless, of MIT, has studied which kinds of corrective actions are meaningful in a corporate context—so you can know that the firms you’re investing in really are committed to saving the planet, or at least to not destroying it. She has found that companies that set long-term emissions targets, have a neutral party oversee their emissions data, tie executive compensation to environmental performance, support government climate-change bills, and set an internal carbon price do best in terms of lowered emissions.

If you like to invest in actively or passively managed funds rather than picking your own stocks, things get even easier. All of the major asset managers offer green mutual funds and index funds, meaning funds that do not put money into extractive industries and that hold companies in their portfolio to certain environmental standards. You can put or switch your money into them with nothing more than a few clicks. And let your fund manager or investment adviser know that you demand green funds: These companies manage gigantic pools of money and large shareholder voting blocs that are powerful influences on the companies whose stocks they hold.

There isn’t much downside to doing this. Green funds tend to do about as well as their conventional counterparts, at least for now. Perhaps the bigger issue is that there’s some evidence that companies in ESG funds do not actually have better environmental practices: There’s a lot of greenwashing going on. The answer for the individual is to do some due diligence, perhaps interviewing your fund manager and making sure that you are comfortable with where your money is going.

But don’t worry about it too much. The symbolism of green investment is more important than the dollars-and-cents effect. As many people as possible need to act like we are in a world worth saving. Becoming part of the divestment movement and greening your 401(k) is a quick and underappreciated way to do that.