Whenever the skill and experience of two employees are relatively equal, seniority shall control in all questions of promotion, demotion, or layoff. When skill and merit are relatively equal between employees, the employee with the greater seniority shall have the first right to obtain or refuse any transfer. When any worker in the industries leaves to accept other employment outside the industries, he shall have the right to return to the industries within one year from the date of leaving and resume his former seniority and employee privileges.