One of the phrases that was coined during the early years of the web was 'content is king'. The basic idea was that content drives traffic to your site. This is clearly correct for the simple case - if you have no content at all you'll get no visitors and when you add some content you'll hopefully get more than zero visitors.
But that was in the days of not so clever search engines. These days search engines don't just take notice of the content on your site, they look at all kinds of other things so there's much more emphasis on using search engine optimisation to optimise content to get as many hits as possible. I don't think there's anything wrong with using SEO and fiddling around with keywords, layouts, titles, URLs and reciprocal linking can certainly help (although it's quite possible to get it wrong as well and lose traffic) but it seems to miss the point. The absolute simplest way to increase traffic to your site is to add more content.
What does this show? I've taken the number of monthly visitors to the site and divided them by the number of pubs reviews on the website. This doesn't give the complete picture of the amount of content on site but I'm not sure how I can work out the number of unique URLs historically. Note, using page views instead of visitors produces a pretty similar graph.
So does it prove anything? I guess if content was the only thing affecting the number of visitors then we'd expect the trend line to be horizontal so there are clearly other factors at work. We've got more inbound links than we used to have (that big spike is when we got linked from another site). I also think age of content helps search engine rankings, although I don't have any proof for this theory. But given that I've done very little SEO work on the site, it does suggest increasing content increases visitors above and beyond a direct linear increase.
As a comparison, looking at the number of visitors to www.doogal.co.uk, where the amount of content has not increased very much, shows visitor numbers haven't increased as dramatically.
To look at it another way, every new page you add to your site will add X new visitors to your site, where X can be anything from zero to a very large number. Adding a new page will probably increase the number of visitors to your site, however small.
So in conclusion, don't waste your time and money on snake oil SEO 'experts', just add some more content to your site if you want to get more visitors.