How do Survey Companies know when to Contact me with a Survey?

Most online research companies you register with will ask you to fill out some "profile enhancers" or will even send you a short survey for their records.

Here (if they haven't already asked this questions during initial registration), questions about your demographic, and questions about what you own, what are you are planning to buy and what your interests are will be asked.

Sound like a lot of personal information? Yes and no. Remember that online surveys are anonymous (read privacy statements on the survey company's website if you feel uncomfortable) and the information they gather about you is only for survey matching purposes. Market research companies compile a database of names and information about the people behind them so as to have the right survey participants at their fingertips. What this means is that if a market research firm is hired to conduct surveys on current vehicle owner attitudes towards car companies, those who don't own a car won't be contacted to participate in this particular survey. How do they know not to contact you? Because of the profile enhancer or short screener they sent you, which asked you this question, and which has also been added to their database.

Think about it: would you want seniors filling out surveys on the latest punk-rock bands? Likewise, would you want teenagers completing surveys on RRSPs? You would receive useless results conducting surveys like this, so it's understandable that survey companies need to select and contact only the appropriate and eligible individuals who qualify for such surveys.
It's also helpful to remember that if profile enhancers are on option to complete on a website, it may be a good idea filling these out. Typically, the more information you provide about yourself, the more surveys you will be invited to participate in.