Empirical research needs data. Scientists are able to collect data through small-scale experiments in laboratories and in many cases by using students as respondents. There are also successful initiatives to collect new data in large-scale longitudinal surveys. The longest-running longitudinal household survey is the Panel Study of Income Dynamics (PSID; https://psidonline.isr.umich.edu/). Other examples include the Health and Retirement Study (HRS); the Survey of Health, Ageing and Retirement in Europe (SHARE); Understanding Society (incorporating the British Household Panel Survey); and the German SocioEconomic Panel Study (SOEP). Access to data is in most cases entirely open, subject to signing a statement governing the use of the data. Empirical researchers benefit from an open-access policy. They have access to a huge number of datasets. However, there are also some problems. Data collection, as in the above examples, is carried out mostly by face-to-face interviewing. This is rather time-consuming, and public release of the data often takes place more than a year after data collection has been completed. In addition, there is little or no room for "outsiders" to add new questions or experimental modules. And although the longitudinal surveys have a multidisciplinary setup, possible new questions must fit the context of the survey. Finally, the large-scale longitudinal surveys all suffer from the problem that face-to-face interviewing has become extremely expensive.