The dependency ratio measures the percentage of the population that’s too young or too old to work.The ratio compares people who are younger than 15, along with people who are 65 and older, to those between the ages of 15 and 64. The ratio can be broken down into the young dependency ratio, which only includes children 15 and younger; and into the elderly dependency ratio, which accounts for those over 64. Suppose a population has 1,000 people. Two hundred and fifty are younger than 15, and 500 are between 15 and 64. The youth dependency ratio would be 50%, or 250 divided by 500. Dependency ratios indicate future economic, social and health trends. A rising dependency ratio means more people are dependent upon the working population. As more people age and retire, and the average lifespan increases, more people count on Social Security and other health and social systems. Meanwhile, there are fewer workers pumping money into those systems to support them.