There is no exact answer to this, and it can depend on many things. The number of survey invitations can depend on e.g. the country you live in. In some countries, there are more surveys available.
The participants are selected through random sampling based on your target group information (such as age, gender, education, profession, place of residence). The target group depends on the settings defined by the survey client.
We encourage you to fill out your profile and background information carefully so that you can receive more invitations to surveys. Survey invitations may also end up in your spam e-mail folder, so make sure that you have checked it. You should add our sender address to your e-mail service’s list of safe senders.