About 80% of the world’s richest philanthropic claim to want to invest in social change, but only 20% do. That well-documented fact dubbed the “aspiration gap” stems from the fact that tackling complex societal issues is far trickier than, say, just donating huge sums to your alma mater or building a new museum wing.

Big complex investments also take time to pay off. In fact, an analysis of 15 major societal changes–from the advent and widespread adoption of CPR to establishing marriage equality–shows that 90% of those efforts took over 20 years of continuous effort to develop, according to Bridgespan, a nonprofit consultancy.

They were also complex: 80% of those ventures required changes to government funding or policies along the way, while 75% involved coordination across numerous industries. And price? The majority also cost $10 million or more. To incentivize major philanthropic funders to keep at it, Bridgespan researchers have developed a “framework for audacious philanthropy,” which was just published in Harvard Business Review.

According to the HBR report, mega-charitable efforts that succeed tend to do 5 main things: Build a shared understanding of the problem and its ecosystem; Create emotionally compelling winnable milestones; Design for massive scale; Drive (don’t assume) demand; Embrace course correction. Any group chasing the next big social good gain should be thinking about these elements as a necessary checklist; the best movements have included all of them, ensuring their massive amount of time and money was being well spent.

From curbing smoking to fighting for marriage equality, some of our biggest societal changes have been backed by big nonprofits in campaigns that have taken decades. Here’s how they did it.

Read more: A Field Guide To Truly Audacious Philanthropy