-SEO provides track able and quantifiable results, regardless of whether you are an ecommerce or non-ecommerce site so there are no qualms when it comes to ROI. SEO agencies are able to track nearly every aspect of their strategy, like increases in rankings, traffic and conversions. Comprehensive analytics also provide the ability to drill down at a granular level and see demographic information and other engagement metrics for individuals who have interacted with your website. For Ecommerce sites, SEO agencies can see which paths users take in order to complete a sale, all the way down to which keyword they used to search for you prior to purchasing. For non-Ecommerce sites, you can attribute values to your lead conversions, like a 'contact us' form fill-out, and calculate the value of your SEO strategy that way.