Gender parity laws, such as 'zipper systems' that require electoral lists to alternate between male and female candidates, are designed to legally mandate gender balance in government. Several European nations have experimented with or implemented varying degrees of candidate quotas to combat historical imbalances and low female representation in parliament. Proponents argue that mandatory parity is a necessary intervention to break up entrenched 'boys clubs' and ensure the legislature accurately reflects the demographics of the population. Opponents argue that demographic quotas violate the core democratic principle of free elections, unfairly punish qualified candidates, and reduce female politicians to statistical tokens.