Which factor could potentially lead to a reduction in an employee's paycheck?

A decrease in an employee's hourly wage directly impacts their earnings, leading to a reduction in their paycheck. When the hourly rate is reduced, every hour worked translates to less income for the employee. This change in wage can be due to a variety of factors, such as company policy changes, performance evaluations, or restructuring of roles within the organization.

While an increase in hours worked typically results in a higher paycheck, a year-end bonus allocation might enhance an employee’s total annual compensation but does not specifically affect their regular paycheck unless stated otherwise. A change in the payroll processing system may impact how the payroll is calculated or processed, but does not inherently cause a reduction in paycheck unless it comes with changes to pay rates or structures. Thus, the decrease in hourly wage is the most straightforward and direct reason for a reduction in an employee's paycheck.