These will help develop new indicators for comparing ageing-related issues and the policy impact of best practices globally. Non-profit organisations such as the American Association of Retired Persons (AARP) in the United States have developed qualitative indicators for liveable ageing societies. These were developed with such stakeholders as community residents, representatives of particular groups and policy makers. Qualitative indicators, on the other hand, should be used not merely to compare results or rank communities, but to collect critical information that cannot be expressed or evaluated quantitatively. Some case study cities apply indicators to understand their challenges better and to monitor the progress of their policies. Cologne monitors the expansion of high-quality educational opportunities for older people, as well as the demand for and supply of social housing.