Final answer:
The number of tax filers jumps between the under-18 and 18-24 group because at 18, individuals typically start full-time work or higher education and gain legal majority, leading to financial independence and the requirement to file taxes.
Step-by-step explanation:
The dramatic jump in the number of filers between the under-18 group and the 18-24 group is likely due to the transition from adolescence into adulthood. When individuals turn 18, they gain legal majority and typically become financially independent, which includes being responsible for filing their own taxes. Additionally, this is the age range where many young adults start their first full-time jobs, enroll in higher education, and begin to earn an income that necessitates tax filing under U.S. law.
Furthermore, students moving into the 18-24 age group may also become eligible for various tax credits or deductions related to higher education costs, which provides additional incentive to file tax returns to claim these benefits. This transition period marks a significant change in legal and financial responsibilities, which is clearly reflected in the increase in tax filers.