Final answer:
The percentage of tax filers has most dramatically increased for the 65+ age group due to increased retirement income, tax incentives for seniors, and longer life expectancy.
Step-by-step explanation:
The percentage of tax filers has most dramatically increased for the 65+ age group due to multiple factors. First, there has been an increased retirement income for this age group, with senior citizens reporting earning 36 percent more income on average than they did in 1980. This is mainly due to better retirement programs offered by private employers and governments.
Second, there are tax incentives for seniors, which encourage them to file taxes. These incentives can include deductions and exemptions specifically designed for older individuals.
Lastly, longer life expectancy has contributed to the increase in tax filers among the 65+ age group. As people live longer, they continue to work past the typical retirement age, providing more opportunity to save for retirement and earn taxable income.