Discussions on reforming the World Bank have typically centered on making the most of existing resources — U.S. Treasury Secretary Janet Yellen’s squeeze-the-lemon approach — and enticing more private sector investment, an even more obvious approach now that former Mastercard CEO Ajay Banga is in charge of the bank.

But there’s one question looming quietly but large in the wings: Whether to give the bank more money, i.e., a capital increase. Many experts say wealthy shareholders will have to put up more if they want to stare down the twin challenges of poverty and climate change, but so far talk has focused on billions of additional dollars.

Now, apparently, we’re talking trillions.

Nine experts, including former U.S. Treasury Secretary Lawrence Summers, were tasked by the Indian presidency of the Group of 20 leading economies to outline a road map for reforming institutions such as the World Bank.

In a lengthy report obtained by my colleagues Vince Chadwick and Shabtai, the experts say that achieving the bank’s proposed “triple mandate” — eliminating extreme poverty, increasing shared prosperity, and boosting global public goods such as climate and pandemic prevention — will require an additional $3 trillion in available capital per year by 2030.

The experts’ report, which backs the ongoing reform efforts, also says multilateral development banks have to get better at drumming up private capital. “Today, MDBs only mobilise 0.6 dollars in private capital for each dollar they lend on their own account,” the G20 authors write. “They should aim to at least double this target.”