Sociologists' choice of research method is influenced by practical issues, ethical issues and theoretical issues. Practical issues relate to time, money and logistics. Sometimes the best method for researching a particular topic, theoretically, has to be rejected because it would cost a great deal of money to conduct, it would be very difficult to carry out, or because it would take a very long time to get results. For instance, researchers considering social change would often consider a longitudinal study, however, the funding body supporting the research may be reluctant to fund such a study as they would prefer to see a timely return on their investment.