How many Coutts are there on Earth?

I don't have an answer but I have made a number of estimates of some orders of magnitude. One thing I am sure of is that it is an uncommon name and the more research I slowly do the more uncommon I realise it is.

I don't suggest my attempts are definitive but rather something to reflect on. If a reader would like to suggest another approach then I would enjoy hearing it.

Calculations for my various estimates are in the attached spreadsheet under various Tabs. Please see the first Tab for an index of subsequent Tabs.

1. An Estimation based on Telephone Directories.

I have begun some searches of telephone directories and applied some assumptions. This work is incomplete

2. An Estimation based on World War One deaths.

I have developed a spreadsheet of all the Coutts who died in the Allied forces in World War One. Based on that, and using some bold assumptions, I have made an estimate as at, say, 1918. Given the changes in the make up of these countries societies, imigration, ethnicity  and replacement rates I am not sure how they can be extrapolated forward

3. Calculations from the website xyz

4. Extrapolations from early Census

5. from the Website ABC

http://gbnames.publicprofiler.org/Map.aspx?name=COUTTS&year=1998&altyear=1881&country=GB&type=name

http://gbnames.publicprofiler.org/Map.aspx?name=COUTTS&year=1881&altyear=1998&country=GB&type=name

6. Any other suggestions??