By assigning citizens to work at their dream jobs (for example: a food stand) you will be able to increase the happiness level at City Hall! The more citizens you have working at their dream jobs, the more your city's happiness level will increase.

However, not everyone has the same dream workplace and thus assigning ones who have their dream jobs to work in Lv.8 buildings of certain categories do not necessarily make them happy. For example, the only way to make Oliver happy is to assign him to work in Lv.2 Digital Storage Disc!