It's more analogous to potential customer numbers. Another good number to track is how long a visitor tends to stay in your site. Webmasters can and should give you information about this. Every website has logs that can be analyzed if the webmaster takes the trouble. I already have a website.
Nobody visits it, and the search engines are ignoring it.
You may be assuming the traffic happens automatically. For one thing, search engines list you only if you tell them your site is there. It's theoretically possible for an engine to find you without you registering, but it can take many, many months. Even if your site is registered, you may appear so far down on the lists that you're invisible. Click here to go to my page on getting traffic.