The methodology I have chosen is to use readily available sources, and to take three time periods or snapshots which can be compared to show the area of origin and spread of  the names CAUSER, CAUSIER, CAWSER and CORSER. The events, sources and times selected are: 

(1) Christenings from the IGI for the period 1500- 1750 - i.e. roughly from the introduction of Parish Registers and covering the period when people generally stayed in their home parishes before the start of the Industrial Revolution brought migration from the country to the towns.
(2)  The 1881 census, when the population throughout the country was recorded, and the mass population movements of the Industrial Revolution were all but over.
(3) The 1999 electoral register, from UK-Info Disk 2000² , for the situation at the Millennium.

That there are shortcomings to these sources is acknowledged, but they do have some advantages. The IGI does not have all parish registers transcribed, so that the distribution will be skewed towards those areas where records survived and were made available. Also, the period taken is one where the spelling of names was not fixed, so that the intermixing of spellings within one family may result in a false picture of origin emerging. However, the source is readily available, and figures are easily extracted. I have taken the number of christenings in the IGI as the measure of population. The 1881 census is the first to be fully transcribed and indexed, so it is easy to extract the figures. By taking the location of individuals on census day, rather than where they were born, I have a snapshot of the spread of the names across the country. The UK-Info Disk 2000 information only covers those over the age of 18 - i.e. eligible to vote - so the total population of each name will be skewed. Also, not everyone over 18 is registered to vote, further skewing the figures. However, it will provide a snapshot of the spread of the adult population over the UK and, again, extraction is easy.

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