Funds can be structured as either open-ended or close-ended. Open-ended funds provide investors with the opportunity, but not necessarily the obligation, to increase their commitment or investment in the fund over time. Close-ended funds have a set, specified size and life. A significant number of unlisted infrastructure funds that have been set up in the past 3 years have been structured as close-ended funds with a total fund life of around 10 years; an illustrative fund life is shown in Figure 13. Some of consequences of this private equity approach are discussed in more detail in Chapter 3.3.