There is one born every minute
There are many fools and dupes in the world.
This proverbial saying is usually trotted out sarcastically when someone shows themselves to be especially gullible; for example:
"I've just had an email from a lady in Nigeria who desperately needed money. I sent her some to help her out."
"There's one born every minute."
What form of dupe it is that is born every minute depends on the time period and location of the speaker. Originally, and in the UK, it was a 'fool'; in the USA and more recently, it was a 'sucker'.
The earliest form of the phrase that I can find in print comes from The European magazine: and London review, published by the Philological Society of Great Britain, 1806:
It was the observation of one of the tribe of Levi, [that is, a Jew] to whom some person had expressed his astonishment at his being able to sell his damaged and worthless commodities, "That there vash von fool born every minute".
The "sucker born every minute" is widely said to have been conjured up by P. T. Barnum. Like many other sayings attributed to Barnum, they are just that - there's no evidence that he coined this phrase.
Whilst probably not having been coined by Barnum "a sucker born every minute" is certainly an American phrase. The first record that I can find of it in print is in The New York Times, December, 1883:
'There's a sucker born every minute,' as the gamblers day.
See also: the List of Proverbs.