Sociology of the family is a subfield of the subject of sociology, in which researchers and academics study family structure as a social institution and unit of socialization from various sociological perspectives. It can be seen as an example of patterned social relations and group dynamics. One of the best known sources for gathering both historical and contemporary data on families is the national census survey. In the United States, the national census occurs in every household every 10 years. There are smaller surveys taken in between called the American Community Survey. Both are held by the larger U.S. Census Bureau and its related subsidiaries in each state. The Census Bureau collects data about American families for the nation, states and communities. Their data provides statistics on trends in household and family composition, and show the number of children, young adults and couples living in the United States. Their wave on Families and Living Arrangements is organized into clusters: childcare, children, child support, families and households, fertility, grandparents and grandchildren, marriage and divorce, and same-sex couples. Another method is ethnographic or participatory observation research of families, which usually reduces the sample size to have a more intimate analysis of the conjugal or other family structure. In general, a qualitative approach to research is an excellent way to investigate group dynamics and family relationships. Specifically, qualitative research on the topic of families is particularly useful when looking at: 1) deeper meanings about family interactions and relationships 2) learning more about the insider views about relational processes and observing interactions 3) looking at the family from within a greater context and 4) providing a voice for marginalized family members (e.g. case of abuse). Often, qualitative data is able to provide ample data that is rich and meaningful, especially for structurally diverse families.