When the Europeans arrived, carrying germs which thrived in dense, semi-urban populations, the indigenous people of the Americas were effectively doomed. They had never experienced smallpox, measles or flu before, and the viruses tore through the continent, killing an estimated 90% of Native Americans.
I think the answer would be causal research. It investigates on an issue looking for an effect of a certain variable to that issue or object. It is focused on the effect one factor to the subject of the research. Hope this answers the question.
The last few decades have seen significant changes in the percentage of women's workforce, especially mothers with underage children, most of whom are working full-time. For example, from March 1975 to March through March 2000, the percentage of mothers with children under the age of 18 rose from 47% to 73%. Thus, According to the data of the U.S. Bureau of Labor Statistics in 2007, this percentage is 71%.
