It's not just moms and dads feeling the pinch of a wobbly economy, as even kids are now seeing less money under their pillows from the Tooth Fairy, a poll by Visa suggests.

In its sixth annual Tooth Fairy Index, the credit card firm says the average American child got $3.19 US for every tooth under their pillow last year. That's down by 24 per cent from the previous year's level.

2015 marks the second straight year that the tooth fairy has left less money since Visa started tracking the "data" in 2009.

To come up with its index, Visa interviewed 4,027 American parents via telephone in May and June, and asked them what the Tooth Fairy left behind if the child lost a tooth and left it under their pillow. A poll of that size has a margin of error of plus or minus 1.5 percentage points with a 95 per cent confidence interval, according to statisticians.

The $3.19 per tooth figure represents $64 for an entire mouthful. That's down from $74 the previous year.

"The Tooth Fairy is finally fluttering back to earth," said Nat Sillin, Visa's director of global education.

Additional findings from the survey include:

32 per cent of respondents said that a dollar was left by the Tooth Fairy, by far the most popular amount.

Nearly 20 per cent of respondents reported that the Tooth Fairy left a $5 bill.

Five per cent of households reported that the Tooth Fairy left $20 or more under the pillow.

Only 1 in 10 parents reported that the Tooth Fairy forgot to leave any money at all when a child lost a tooth.

For the second year in a row, fathers reported a far more indulgent Tooth Fairy, saying that dads left nearly 30 per cent more than what moms did: $3.63 vs. $2.87. Dads polled by Visa have reported a more generous Tooth Fairy every year that Visa has tracked the question.