An international group of researchers came up with a comprehensive ranking system for 18 different OECD countries to assess the quality of life of aging populations. Their metric, called Aging Society Index, included five main factors: security, cohesion, well-being, equity, and productivity and engagement. All of these factors are on a scale out of 100, and are weighted based on their importance (each was about a fifth each). Taken together, these factors show that aging populations need to be integrated into their societies with access to resources and care. The work was published in the Proceedings of the National Academies of Sciences earlier this year.