The disability caused by a given disease or health condition is determined through complex economic-type mathematics that looks at functionality, a discounting of future years of life and other complex factors. The idea with DALYs is that public health officials could use these scores to allocate funding with the goal of limiting total suffering.
DALYs allow researchers to compare across diseases. For example, because future years of life are discounted, 3,300 DALYs would equal 100 infant deaths or 5,500 people aged 50 living one year with blindness. These comparisons are helpful in setting national and global health priorities.
Sources:
World Health Organization. Disability adjusted life years (DALY).

