I'm most familiar with the Dutch system. The Dutch government first gave a tax benefit to institutions that created funds that enabled citizens to make types of impact investments. They weren't necessarily development funds. They could also be environmental funds. In the end, four funds were created by different banks. These include the Triodos Bank and the ASN Bank. Various financial institutions established these funds, which are mutual funds. Therefore, any citizen can buy shares. The funds are then invested according to the institution's mandate, while meeting the conditions imposed for entitlement to the tax benefit. In the case of the ASN Bank, a mutual fund was established in which people could buy shares. Unless I'm mistaken, the fund is currently about 70 million euros.
At first, investors had a tax benefit. People could deduct their investment, or the interest received on these investments. After several years, the tax benefit was eliminated. However, the contributions didn't decrease. Instead, they continued to increase. The tax deduction provided an impetus to establish the funds, which then continued to exist.