The Total column shows the total number of people in that county or town with this surname.
For example, there were 17,490 people called ISAACS in St Martin In Fields at the time of the 1881 census.
The Frequency column shows the percentage of people in this county or town
with this surname. For example, a frequency of 17.2551 in St Martin In Fields means that
17.2551% of the people in St Martin In Fields on census day were called ISAACS.
The Index column shows the relative probability of finding someone called ISAACS
in this county or town, compared with the probability of finding them anywhere in Britain as a whole.
An index of 1 means that if you pick someone at random from this county or town, you have exactly the same
probability of picking someone called ISAACS as if you picked at random from the whole of the UK.
Where the index is higher than 1, then you are more likely to find someone called ISAACS here
than if you picked from the UK as a whole, and where it's lower then you are less likely. The actual figure
shows the level of probability - for example, a figure of 2 would indicate that you are twice as likely to find
someone called ISAACS here than in the UK as a whole, and 10 would make it ten times as likely.
The value of 17.49 in St Martin In Fields means that you are 17.49 times as likely to find
someone with the surname of ISAACS in St Martin In Fields than you would be in the whole of the UK.