There’s a new gauge for traders wondering when it’s time to buy the dip. And for now, the sign says not yet.

Money’s flooding into exchange-traded funds that buy Treasuries with a duration of less than one-year, boosting the size of a State Street Corp. fund that holds T-bills to a record.

It’s an indication that with the S&P 500 Index suffering through its worst year since 2008 and returns on short-term government bonds not that different from those that mature in 10 years or more, investors are choosing cash and cash-like instruments over stocks.

While bond ETFs are a small part of the overall fixed-income market, traders are increasingly looking to them for a real-time indication of sentiment, thanks to their daily transparency about flows and holdings. So it stands to reason that some are using short-dated debt ETFs as a lens into the most volatile year since 2015.

“Money talks,” said Will McGough, chief investment officer for retirement investment strategies at Stadion Money Management, which manages about $3.2 billion from Watkinsville, Georgia. “Especially with ETFs, it’s a sample for the wider market ecosystem. You can certainly watch short-term ETFs to see when those cash flows start heading out.”

State Street’s fund -- the SPDR Bloomberg Barclays 1-3 Month T-Bill ETF, ticker BIL -- is poised to absorb more than $1 billion of assets for a third straight month. The fund previously took in more than that just once, in August 2011, as investors reeled from Standard & Poor’s downgrading the U.S.’s AAA credit rating for the first time.

Meanwhile, the iShares Short Treasury Bond ETF, ticker SHV, has more than doubled its assets under management this year, gathering more than $12 billion. Half of that came in the first half of the year when rising interest rates fueled a bid for short-term debt, but the fund took in $1.7 billion last week, its best five-day period in almost three years.

In many ways, the recent popularity of these funds could be a case of investors wanting to avoid everything else, according to Matthew Bartolini, head of Americas research for State Street’s ETF business.

“You’re sort of knowing that you’re just parking your money to play a defensive-like approach,” Bartolini said. “If we start to see outflows from BIL, that’s a result of the market rebounding significantly and all of a sudden these trend-following strategies going risk on.”