Previous disaster studies in Taiwan are quite limited until the 921 earthquake. After the earthquake, however, most research analyzed victim-only samples suffering from selection bias. This article compares three earthquake-related surveys and illustrates their limitations. Taiwan Education Panel Survey with nationwide high school students samples is not a random sample of the national population and biased by some retrospective errors. Collected through telephone surveys, Social Image Telephone Survey may lose victims who were damaged too much to keep a household telephone. Finally, House Reconstruction Database was constructed by coding the information of the applicants for the House Reconstruction Project of the 921 Earthquake Relief Foundations. However, the requirements of the applicants may lead to the self-selection problem. These results imply that the limitations of the datasets have biased the statistics of disaster analyses. Therefore, we suggest the government and relative relief institutions shall conduct a victims' census after each disaster to support Taiwanese disaster studies in the future.