Immigration
Every year, between two and three percent of the world's population is on the move, hoping to find better opportunities by moving to new areas. The factors affecting where and when people move can be categorized broadly as either push or pull. Push factors motivate people to leave an area, while pull factors attract people. These factors often work together. For example, low wages in one country may push people to move to a new country with higher wages, while the new country's higher wages will be pulling them. Education works similarly. A lack of access to higher education is a major push factor for young people all over the world, and they are pulled to countries with the well-respected universities.
Immigration is key to the prosperity of many Western nations. The average age of Western populations is rising, as families have fewer children. Moreover, experienced workers are retiring each year, with fewer young workers to replace them. Economies need new workers to grow, and many western economies would collapse without immigration. Competition for immigrants is on the rise, and developed countries are trying to increase their pull by providing good job opportunities and generous support services, such as occupational and language training.
What does them in the second paragraph refer to?
A. families
B. children
C. young workers
D. experienced workers