Am I right in thinking that this phrase is not quite as ubiquitous in the States as it was in the 80s and 90s? (I’m basing this on evidence from US TV and movies, not the most solid of bases, I admit). If so, has it been replaced by anything?

And when did the phrase begin to gain such popularity? I realize that variants such as ‘Have a good day’ are as old as the hills, but it’s the rise of the nice one that interests me and its sudden dominance over the tongues of all in the service industries, which I think I became aware of in the late 70s. (It gained a small foothold in the UK but thankfully never took real root here.)

I first realized that service people at the casinos in rural Nevada were saying “Have a nice day” sometime since 2001. I have no feel for how long they have actually been using this expression. Many of the service employees who have trained in the last couple of years use this expression.

The older casino employees still say “Good luck.”

The OED2 has a 1971 citation that indicates it was an American cliche by that time.

I once read an explanation/hypothesis for the rise and spread of “Have a nice day”. I can’t find it now, and I don’t know if it is true or a just-so story.

Imagine a customer going through the checkout line at the supermarket, or paying the check at the diner counter. The old fashioned custom calls for a “Thank You - You’re Welcome” to punctuate the ending. However, it has become more common for customers to drop the “thank you, etc.” and go through the transaction silently. The absence of the usual formality leaves an awkward gap that salesclerks filled with “Have a nice day” to punctuate the otherwise silent ending.  According to this theory, it means something like “You didn’t say ‘thank you’, so I didn’t get a chance to say ‘you’re welcome’, but I need to say something to acknowledge we are done with this brief transaction.”

I’m not sure why one would want to thank a sales clerk for checking one out at a supermarket. We have an arsenal of mumbo-jumbo phrases for casual encounters of this kind: “good morning”, “hello”, “hi”, “good-bye”, and (absolute bottom of the barrel as far as I’m concerned) “have a nice day”. You can see people using them without even making eye contact."Thank you” is a phrase I like to reserve for occasions when it means something. But this is pure idiosyncrasy, I suppose. I still have a tendency automatically to mutter “sorry” when some careless oaf jostles me in the street............

Yes, the number of “thank you"s that a single payment at a shop or supermarket generates always amuses me.  The count can go up to five or six, especially if the shopper is thanked for shopping at Tesco’s or whatever.  I tend, like you to reserve “thank you” for when I’m actually given something, like my change.  The amount of insincere corporate thanking and welcoming one is now subjected to is reaching alarming proportions.  I was not at all gratified yesterday to find that the council had spent several thousand pounds of mine and other taxpayers’ money on replacing a perfectly good street sign with one twelve foot high welcoming me to one of their industrial estates.