It can be helpful to be aware of potential sampling bias in data. If you wish to explore this topic further, the following research can be a good starting point:
This guide is designed to help you find data and statistics for your research or studies.
Be aware that data is only available if someone has collected it and they are prepared to give you access to it. In some cases, access is restricted because data is commercially sensitive or contains personal information. Other data is made available under licence and requires registration before access is granted. Today much data is freely available online but there is still much data that is not free. The Library buys some data and statistical publications, but we can’t buy everything. If data is essential to your work, allow plenty of time to find it and be aware that it may not be available to you.