If you really want to understand the effectiveness of SEO from a scientific standpoint, read Search Engine Optimization: What Drives Organic Traffic to Retail Sites? from Journal of Economics & Management Strategy, Volume 25, Number 1, Spring 2016, 6–31
I know. The piece is a bit old by Internet standards, but the more one reads it the more one learn. Baye, De Los Santos, & Wildenbeest have done a great research publishing their findings. The study was sponsored by Google, a few years ago.
It is still very relevant to search marketers and prospective clients.
My favorite piece from their findings is this:
“While previous literature has focused on the role of sponsored links in consumer searches, Michael R. Baye, Babur De los Santos, and Matthijs R. Wildenbeest are the first to explain the drivers of organic (natural) clicks to improve search engine optimization (SEO). In this interview, the authors discuss why investing heavily in brand equity, instead of exclusively on search rankings, is crucial for a retailer’s SEO strategy. ”
“We also point out that investments that improve site quality and consumer awareness (and more broadly, that enhance an online retailer’s brand equity) are likely to have spillover benefits in other channels that are not accounted for in this or other studies of organic and sponsored search. These benefits include increases in clicks through other online channels (such as price comparison sites), increases in the number of direct visits to a retailer’s website, increases in visits through navigational searches at search engines, and increases in traffic at the retailer’s physical stores. These considerations–coupled with the fact that position is a zero-sum game and thus a retailer is unlikely to obtain a sustainable advantage through direct efforts to improve its ranking–lead us to conclude that brand equity is one of the more important components of retailers’ SEO strategies.”