My rule of thumb to figure out which search engine has the largest share of customers for your product

As simple as it is, i thought it would be helpful to share

Step 1: List up your search engines

Step 2: List up keywords that are relevant to your brand or product

Step 3: Compare the search volume for each search engine

Step 4: average it out and determine for yourself which has the higher share of customers

What do you guys think?