1. Selection criteria: Many enterprises usually regard education as an important selection criterion when selecting employees in management positions or other senior positions. If education is a necessary condition in the company's selection criteria, employees who fail to meet the education requirements may lose the opportunity of promotion.

2. Knowledge level: Although academic qualifications do not fully represent employees' knowledge level and working ability, in some industries and positions, highly educated employees usually have more academic knowledge and professional skills, which will also affect employees' promotion to some extent.

3. Corporate culture: Corporate culture may also affect employees' promotion opportunities. Some companies pay more attention to academic qualifications and think that highly educated employees represent the company's brand image, so they are more inclined to promote highly educated employees. However, some companies pay more attention to employees' actual work ability and performance, so they are more inclined to promote those employees who perform well.

4. Talent mobility: In some industries and fields, talent mobility is relatively large, and highly educated employees are more likely to be poached by other companies, so some companies may be more inclined to promote highly educated employees to retain talents.

The influence of diploma on promotion may be the result of many reasons. In this case, employees can actively participate in the company's training and learning by improving their work ability and performance, improve their competitiveness and increase their chances of promotion.