Parties can develop from existing divisions in society, like the divisions between lower and upper classes, and they streamline the process of making political decisions by encouraging their members to cooperate. Political parties usually include a party leader, who has primary responsibility for the activities of the party; party executives, who may select the leader and who perform administrative and organizational tasks; and party members, who may volunteer to help the party, donate money to it, and vote for its candidates. There are many different ways in which political parties can be structured and interact with the electorate. The contributions that citizens give to political parties are often regulated by law, and parties will sometimes govern in a way that favours the people who donate time and money to them.