## 6 Conclusions  
### Contributions  
This study proposes a staff scheduling strategy to minimize total labor costs considering the actual features of the Korean construction industry, such as an increase in labor costs and the change in labor policy. The contributions of this paper are as follows. First, this paper suggests a mathematical model that can save the total labor cost and aid the management of human resources. As shown in the numerical experiment, a mathematical model decreases the unnecessary number of employees from about 46.6 to 45 a day on average. This can allow a company to have an opportunity to save labor costs and rethink and optimize the number of employees they should have. Second, the practicality to apply the developed mathematical model to other industries is proven. This study considers an actual construction company suffering from the problem of no-show, derived from the situation that the company increases irregular employees to handle workforce shortage due to the rise of labor costs and a new labor policy in Korea. Through the numerical experiment with system parameters derived from human resources, types of jobs, workplaces, and the rules of work of a company, the applicability of the developed mathematical model to a company is proved in practice. Therefore, this paper would help conduct research on staff scheduling for the actual company as one of the basic references. Third, the change in labor policy is considered when developing a mathematical model. The optimal solution for staff scheduling by using this mathematical model is derived in the situation of workforce availability reduction compared to the same number of employees due to the influence of changed labor policy. In other words, this paper could play a role as a guide for staff scheduling that must consider the change of labor policy in the future in Korea. Lastly, this paper assists the manager of a company with decision-making for staff schedules by providing various proactive cases while considering the sudden absence of employees. Despite the difficulty in considering unpredictable employee absence due to the inherently uncertain nature of irregular employees, additional numerical experiments, which are the simulation and sensitivity analysis, are performed in the paper. The result of the simulation predicts what expectedly happens when assuming the application of a deterministic staff schedule in practice. In particular, the predictive information on how many irregular employees would not come to work is given. It is impossible to guarantee that they would follow staff schedules perfectly in the real world. Nevertheless, the reason to perform the simulation is to allow managers to have a systematic procedure to respond to the absence of irregular employees, not to provide a staff schedule that makes all irregular employees follow the staff schedule. Moreover, through this sensitivity analysis with the change of the average percent of absence, this paper observes the influence of irregular employee absence on the change of the value of the objective function and staff schedule. Through the additional numerical experiments, various proactive cases are provided by considering the absence of irregular employees. This can help managers prepare the precautious measures to respond to the stochastic irregular employee's absence. Thus, it is expected to contribute to helping the manager with decision-making for staff schedules.