One quick way to find statistics on the web is pretty simple: search for your topic and "statistics." (Of course, be sure that the sources you find this way are reliable and check for bias.) You can also go to specific resources that provide statistics in certain areas.
Some examples and suggestions:
Another key question to ask yourself: Who would collect statistics on this topic? A government agency? An advocacy organization? If you can identify a potential source, then going directly to that source's website can help you find relevant statistics.