If you are looking for stats then this article in the SEOTribunal is a great place to start.

If you too rely on Google’s traffic as the main source to attract new customers to your business, it is very likely that you have faced the consequences – both good and bad – of the fact that SEO is always changing.

As algorithms change, certain approaches to SEO become more powerful than others. This in itself means that businesses need to be aware of what works in SEO and what does not, in order to avoid being penalized by Google.

Here’s just a teaser:

• 67k searches are performed on Google every second
• 39% of all global e-commerce traffic comes from search
• 93% of all online experiences begin with a search engine
• Nearly 80% of users ignore paid ads in search results
• 50% of all searches will be voice searches by 2020

For more go read the original article