The article of the Economics (April 26, 2014) titled “Demography, growth and inequality; Age invaders” ends up with the following passages:

It (shift to ageing population) will be a world in which ageing reinforces the changes in income distribution that new technology has brought with it: the skilled old earn more, the less-skilled of all ages are squeezed. The less-educated and jobless young will be particularly poorly served, never building up the skills to enable them to become productive older workers. Compared with the dire warning about bankrupting consequences of a gray tsunami, this is good news. But not as good as all that.

I think “Gray tsunami” means global and quantum increase of the aged population, and find it an interesting wording.

But is “Gray tsunami” an acknowledgeable set of words to describe accelerating ageing of global population to the point, or just a one-off coinage invented for this article?

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    It is a coinage that has achieved some degree of recognition and repetition. It's not a "word", but two words which are perfectly valid on their own. (English only very rarely regards two separate character strings separated by a blank to be one "word".) – Hot Licks Dec 7 '14 at 2:30
  • Have you looked up some dictionaries to check if it's "an acknowledgeable (did you actually mean "acknowledged," or was that intentional?) word?" (Btw, it's not a "word" incidentally.) – Kris Dec 7 '14 at 5:39
  • @Kris. Kenkyusha's Readers' Plus English Japanese Dictionary (the 2nd edition) which is the most popular English Japanese dictionary in our country shows "acknowledgeable" as a derivative adgective of acknowledge. Google Ngram shows usage of "acknowledgeable" at 0.0000003619% level in 2000 though it dropped to a half from 0.0000007619 in 1970. I checked it before posting this question.I edited the "word" in the question in responce to your and Hot Licks' comments. – Yoichi Oishi Dec 7 '14 at 7:42
  • That effort was not called for at all, "acknowledgeable" is a word, of course. However, it does not mean what the context requires. – Kris Dec 8 '14 at 6:31

The easiest thing to do is look for other uses, and if you do so you'll see that it is indeed used. Note though that while there are other uses, there aren't a lot. Silver tsunami is more commonly used of the same thing, though still not very common. It's perhaps best thought of as a minor buzz-phrase that a lot of people will use, and those who don't know will understand due to the metaphor being clear, but not something everyone will have in their productive vocabulary. (Or for that matter, be happy with if they do know it, there are objections to the metaphor, not least that an unpredictable event like a tidal wave* is not an appropriate metaphor for a demographic shift that's been easily foreseeable for decades).

It also appears to be a largely American use, though other English-speaking countries have similar issues (though not all countries do, or do to the same extent).

It refers primarily to the effect on the employment patterns, social security and health of a given economy rather than just the numbers themselves. (A rather old-fashioned use of quantum in most dialects, incidentally, though still popular in that sense in Indian English).

*Incidentally, whether figuratively or literally, poor old "tidal wave" is a phrase that got an unfair bad rap just because tidal waves have nothing to do with tidal activity, and so the loan-word tsunami has all but entirely replaced it. Really, since tidal waves are indeed waves that look like an incredibly low then high tides of great suddenness the term is perfectly apt, while they are in no way restricted to harbours making tsunami the choice that has the weaker connection to the reality. The only thing that makes tsunami seem more accurate is that most English-speakers don't know what tsunami's components mean.


The use of "tsunami" as a metaphor increased after the Indonesian/Indian Ocean tsunami of 2004, possibly because this previously generally less familiar word now had many more people who understood it. A quick check online now indicates that "silver tsunami" and "gray tsunami" (both essentially a more striking way - a 'colourful phrase' - to say "ageing population") has been in use since at least 2010 - search for comment by novelist Martin Amis (in 2010) and article by Philip Longman (in 2010). See Economist article from February 2010: http://www.economist.com/node/15450864


The term "gray" is sometimes used to refer to old people. From Wiktionary:

Relating to older people.

This is because some people's hair goes from being black to gray as they get older.

One example of this is grey nomads being used to describe retired people travelling from place to place in Australia.

The term "tsunami" is used metaphorically. Basically, it means a change or phenomenon that is very large in nature. I can't find this usage in Wiktionary, but I can find wave being used this way, and a tsunami is even larger than a wave:

(figuratively) A sudden unusually large amount of something that is temporarily experienced.

  • A wave of shoppers stampeded through the door when the store opened for its Christmas discount special.
  • A wave of retirees began moving to the coastal area.
  • A wave of emotion overcame her when she thought about her son who was killed in battle.

From Wave of protest over tsunami of metaphors, a somewhat humorous complaint about the use of metaphors:

Have you noticed the tsunamis coming at us from all directions? Have you been submerged in a tsunami of tedium?

This tsunami emerged slowly after 2004 when the big tsunami hit on Boxing Day, but since a tsunami hit Samoa in 2009 then Japan two years ago, there has been nothing but a tsunami of metaphorical tsunamis.

Open the newspaper to be confronted by somebody's extreme sadness, which we now must label a ''Tsunami of Grief'' (London Telegraph, November 2012), but this uber-grief must compete with the same tsunami being responsible for so many other modern calamities, including poor development practices in a ''tsunami of concrete''.

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