Seniority is a system of job allocation and EMPLOYMENT protection based on how long an employee has worked for a company. The length of continuous employment until resignation, transfer, discharge, or LAYOFF often defines seniority. Seniority systems are most prevalent in UNION and government work environments. There are many detailed, legal aspects of seniority, dividing it into categories of employment, series, and class. Employment seniority concerns the original date of hire into a company. All transfers, promotions, and discharges are usually based on employment seniority. Series and class seniority results in exceptions to the employment-date seniority. Laws regarding seniority vary by state laws and corporate rules. Series seniority is the number of continuous months (of qualifying service) as a regular employee in a series. A class is usually a specific work section within a series. For example, an electrical worker would be part of the electrical series, but may work in the high-power section, which would be a specific class. His seniority would be based on his class, the high-power section, rather than as part of the series, electrical workers. When a person transfers to another section (class), they become the most junior person in that class. Series and class seniority affects job activities and, more importantly, layoffs. A worker with significant time as an electrician but is relatively new in the high-power section could be laid off before someone who has less time as an electrician but more time in the high-power class. Similar seniority rules are applied to REDUCTIONS IN FORCE (RIFs) of public-sector employees. Just as there are different ways to classify seniority, there are different ways to lose it. Employees may lose seniority through quitting, resigning, discharge, release, retirement, transfer, or not returning to work when recalled from a layoff. When a recall occurs, the most senior person in the class is the first rehired. One problem with seniority systems is they discourage workers from changing classes, especially during periods of economic decline. This can contribute to boredom and job dissatisfaction, lowering morale and productivity. Another problem is that seniority can prevent an employer from hiring or promoting the most qualified person because someone else with greater seniority has to be given the position ahead of a junior person. In addition, there is the question of what to do with the seniority system when companies merge. Do employees from one company have seniority over the employees from the company with which it is being merged, or is seniority based on length of service to either company? Economists are usually critical of seniority systems in that they discourage efficient allocation of RESOURCES. Workers in seniority systems counter that the systems encourage worker loyalty and prevent employer discrimination against older workers.