As always, rising costs in material, wages and transport, has had an effect alongside falling sales. The cheaper, and not as good, versions from elsewhere, I probably mean China, has led the decline in sales.
Sold cleverly by the use of women holding 'Tupperware Parties,' and gathering all around for a natter and sales, the company blossomed during the 50s and 60s when income increased and those without fridges found the tightly closed boxes useful for storing foodstuffs.
The party however, is now over.
Plastic remains elsewhere however...