Where does the Tooth Fairy get all that money she leaves under children’s pillows? The original source of that wealth remains a mystery, but the evidence suggests that she keeps it invested in the U.S. stock market.

Delta Dental has tracked Tooth Fairy payouts since 1998. The results show an uncanny correlation with the S&P 500 index, suggesting the Tooth Fairy has less to hand out when the economy is hurting.

The average payment per tooth in the US was just under $1.50 in 2000 when the S&P was at 1,300. In 2017 as investors celebrate the S&P record of nearly 2,400, children join in the festivities by reporting Tooth Fairy payouts of $4.66 per tooth. For 12 of the past 13 years the Tooth Fairy payout has tracked with the movement of the S&P 500.

US children are not the only beneficiaries of the Tooth Fairy’s generosity. Children in the following countries can reasonably bank on receiving these payouts:

• Brazil: R$14.47 ($4.69 USD)
• Canada: $6.11 ($4.56 USD)
• Costa Rica: ₡2,613.42 ($4.68 USD)
• Ireland: €4.38 ($4.72 USD)
• Japan: ¥525.82 ($4.72 USD)
• Spain: €4.38 ($4.72 USD)
• United Kingdom: £3.75 ($4.67 USD)