Two brief comments (of no realimport):

Q,
"...Someone mentioned the use of collective plurals.
In the UK, 'the army are' seems to be used; in the United States, it is 'the army is', and the same is true of some other collective plural usages.
When did the Americans shift over from "The United States are..." to "The United States is..."?

Mr Red,
"...and while we are at it - what is the plural of data?..."
Data IS the plural, the singular is datum.

Merry Christmas all.

Walrus.