(Bloomberg) -- Investors of exchange-traded funds that buy U.S. government debt are signaling that economic-growth optimism is taking root.

After pouring into the ETFs to start the year, investors pulled $10.3 billion in March, the biggest exodus since December 2010, data compiled by Bloomberg show. The $7.86 billion iShares 1-3 Year Treasury Bond ETF alone lost a third of its assets from withdrawals, the most of any fixed-income fund this month.

Subscribe Now

Access to premium content including in-depth coverage of mutual funds, hedge funds, 401(K)s, 529 plans, and more.

3-Week Free Trial

Insight and analysis into the management, marketing, operations and technology of the asset management industry.