This is a great question! I can see why it’s a tricky one for many to answer, since there are so many factors involved. I can’t just give you a yes or no answer.
For instance, if your site is *improperly* optimized, i.e., it’s optimized for keywords which nobody is searching for (the way many unprofessional SEO companies optimize) it certainly won’t help your sales. Of course, it won’t help your traffic either.
Or how about this scenario: let’s say you do increase your traffic, but it’s for words that are really general. Like, say you sell real estate in Boston, and you get a number-one ranking for the general keyword “homes.” (It’s probably not gonna happen, but just bear with me for illustration purposes!) You may certainly get lots of traffic from that “great” ranking. But how many of the people who type “homes” into the search engines are actually searching for homes in Boston? Chances are, probably not too many. Casting the widest net in this manner is not usually the best way to approach things.
However, what if you optimize the same site for “Boston Real Estate” or “New Homes Boston” and other highly specific keyword phrases that relate to the business and exactly what the site offers? Traffic should go up compared to a site that is not optimized for those phrases. Plus, most of the traffic should come from a very targeted segment of the population, i.e., those looking for information on Boston real estate.
Assuming you have a great site that is professionally written, and you also have great salespeople who give terrific customer service, the end result should be more sales. But again, there are too many external factors to make this a “gimme.” What if you have a really crappy site? Perhaps it looks like your neighbor’s nephew designed it; or maybe there’s no “About Us” info to help build trust and credibility. Or maybe the site is riddled with typos and poor grammar. You may get a huge increase in traffic from your search engine optimization efforts, but no additional sales because your site visitors surfed away in dismay.
So let’s say you work really hard on your site to make it the best it can be. If the people that answer the phones are rude or ignorant — again — no sales increase. Or perhaps you don’t have enough phone operators to handle the influx of business that your high rankings suddenly bring you. (I’ve had this happen with one client.) Then your SEO work is simply a waste of time and money.
So, I really can’t answer your question other than to say that if you do everything right, you can bet your behind that a good SEO campaign will bring more sales. Absolutely, positively no question about it. But if you miss any of the important factors that go into creating a good Web site and a good business in general, you may not see an increase in sales. This is why I’ve been spending so much time talking about site usability issues lately. High rankings are only as good as the usability and overall effectiveness of your site, your employees, and your business in general.