Developing and promoting tourism products takes the resources of people, time, and money. Therefore, mistakes need to be avoided. Even though those developing the tourism sector will understand their product, they may make assumptions as to the desires of visitors. Tourism marketers must learn what potential tourists need and desire from the visiting experience and the only way to obtain this information is by conducting research. Tourism researchers frequently need to know how many people are visiting a city and for how long they are staying. Quantitative research should also be conducted to determine who is visiting. Depending on the need, the research may gather demographic data on age, gender, or ethnicity. Other research may focus on geographic data such as where the visitor lives. Descriptive research studies are used when the research question asks for specific statistical demographic data on tourists.