Is there any benefit for having multiple copy of a same luxury resource?

Question

I'm pretty new to civilization 6 and its amenities system

One thing that is for sure is, one luxury resource yield 1 amenity point to the first 4 cities that need it the most. The question is about the 2nd copy of this luxury resource, would it extend to the next 4 cities ?

There seems to be this belief going around that having multiple copy of luxury resource will have its benefit provided to the next 4 cities. I had this belief too, implicitly, before even researching online about this matter; it make sense to be so after all.

However, from my very crude testing, it seems that multiple luxury resource does not yield its point to the next 4 cities and thus having multiple copy of luxury resource doesn't seem to have any benefit other than trading them off with another civ. However, my test is very crude and I'm not too sure if there is any other condition affect this amenity thing so I'm not too sure about this test. Does any one have any idea about this matter ?

Edited according to @scottn and @Michael Campbell's answer:

• Before world congress was introduced multiple copy of luxury resources do not provide additional amenities.
• After world congress was introduced multiple copy of a luxury resource can provide additional luxury point if the world congress has voted for that luxury resource to be so.

Answer 1

According to what I can find in several online Civ VI wikis, your testing is correct. A luxury resource type provides it's benefit once, and additional copies do not increase this, but I will check the official sources for confirmation.

While the in-game Civilopedia does not explicitly spell it out, it does seem to agree:

"Each type of Luxury resource can contribute up to 4 Amenities to your empire (1 per city) to the 4 cities that need them most."

But it is explicitly stated on page 50 of the Civ VI manual:

"Only one source of a specific luxury provides amenities, shared with the four neediest cities in your empire. For example, if you have 2 Citrus resources improved around your capital, only the first will be providing amenities to your empire. You can choose to trade the second Citrus with another civilization for something else you need, like Gold, or another resource."

https://downloads.2kgames.com/civilization/vi/manuals/eu/CIV_VI_25TH_ONLINE_MANUAL_AUS.pdf

Answer 2

Seldom-seen edge case: the World Congress might bring up the question of tweaking a luxury resource. Civs vote on which resource to tweak, and if it should provide zero amenities, or instead if multiples per civ should provide extra amenities. So for those 30 turns, you might be able to make use of two citrus to provide an amenity to 8 cities.