This process can be thought of as constituting a series of waves. The first wave begins when A temper in population growth caused by decreases in fertility (which can be brought on by matters such as more access to birth control, rising incomes, urbanization and higher levels of education for women) helps to stimulate a significant shift in the age distribution of the population towards those of the working age (but at a later stage decreases in mortality and fertility will cause an aging population). This shift is able to accelerate economic growth as the working age population increases while the (relative) number of dependent children declines.