Johanna Rubba wrote:

> As to the difficulty of the range of concepts to which <-'s> is applied,
> I don't think it's all that difficult to teach. (Of coures, we don't
> have to teach the meanings that the affix represents; native speakers
> already know this, albeit unconsciously. What needs to be taught is the punctuation.)
>
> Possession is a central or prototypical use of <-'s> that students can
> readily  understand. It can then be extended to other cases.

I have no idea what "central or prototypical" means here.  If it means
more occurrences in a given corpus of written English, then I would
agree.  However, let's think about the confusion which writers of
English might have with the apostrophe-s.

There are three uses of the apostrophe-s ('s).

1)  Indicating a close relationship between one noun to another.  I
don't like the
use of the term possession. I don't think we would want to tell anyone
that the relationship of Bill to mistress and critics is the same in the
following constructions. (If that relationship is the same, it is only
in the most metaphorical sense of a very particular kind.)

         Bill's mistress
         Bill's critics

2) Indicating missing sounds.

        It's a boy!
        Bill's gone too far.

3) Indicating plurals

        1) The word after 'is' is mi--ing two s's.

Uses (1) and (2) are in conflict with regard to its and it's. And, use
(3) conflicts with the plural-s, sans apostrophe.  Use (3) also may
cause confusion for decades 1960s or 1960's and other kinds of numbers.

I have no way to measure it, but it's possible that one's exposure to
all three -s's is very frequent.

As Johanna has already pointed out, use (1) may be undergoing change.
In the student union at my university, there is a room labeled

        a) Presidents Gallery

I think that is different from

        b) President's Gallery
        c) Presidents' Gallery

It might be interesting to speculate what one might expect to find in a
room labeled with (a) as opposed to (b) or (c).

I wonder what the evidence there is for the following is.

> And if
> reading as a habit and hobby continues to decline, teaching the rule will
> probably not be very effective. Also, if public media begin to present
> examples that violate the current rule, even reading will not be a
> corrective.

My understanding is that book sales are up.  A greater percentage of the
population is reading more than ever. I also suspect that the growth of
the internet has increased the amount of time a certain percentage of
the population is interacting with the written language.  I know that in
the last 10 years I am writing more every day than I used to.

Bob Yates, Central Missouri State University