Yes, Bond ETFs Can Go Haywire. But That's a Good Thing, Says BIS

Critics of the passive-investing boom in bonds warn about the risks stemming from the mismatch between highly tradable ETFs and the illiquid securities they hold.

Turns out this very discrepancy might help stabilize the market, according to the Bank of International Settlements.

The latest quarterly report from the Basel-based central bank for central banks explores the mechanism that regulates the price differences between fixed income exchange-traded funds and the bonds they own.

The surprising conclusion: Yes, the two values can be wildly different, but that disconnect is a key shock absorber for the market.

When money flows into an ETF, a market maker known as an authorized participant (AP) buys more of the assets the fund holds and swaps them with the issuer for new shares. When cash flows out, that happens in reverse.

The BIS found that the bucket of securities exchanged for shares in a typical aggregate bond fund matches just 3% of the ETF’s holdings. That basket can change dramatically from day to day, and even differ from AP to AP. It’s this very elasticity that gives bond funds their resilience.

“The flexibility inherent in baskets’ composition may allow ETFs to withstand episodes of market stress,” the BIS’s Karamfil Todorov wrote. “In the face of panic selling (runs), which generates redemption pressure, ETF sponsors could tilt redemption baskets towards riskier or less liquid securities. This would decrease prices of ETF shares since shares are exchanged for a lower-quality subset of ETF holdings.”