Is strong typing worth the cost?

[dmjones <derek@NOSPAMknosof.co.uk>]

All,

I have been trying to locate evidence that the cost of the use
of strong typing is repaid by a greater benefit.

Now we all know, from first hand experience, the benefits of
strong type checking.  But where is the experimental proof?
I know of two studies:

A Controlled experiment to assess the benefits of procedure
argument type checking, by Prechelt & Tichy, IEEE Trans on
Software Engineering Vol 24, no 4. 302-312.

An Experimental evaluation of data type conventions, by Gannon,
CACM Vol 20, no 8. 584-595.

Both studies used student subjects, not the one most likely
to have had lots of experience structuring a program using types.
One study also used C, which is strongly typed if compared
to assembler.

So where are the studies showing that strong typing in Ada (or
Pascal) saves money/time, creates more reliable programs, etc?

References anybody?