An index tracking the most expensive stocks to borrow has risen by a third since February, its owner says, pointing to a rise in short selling activity.

New York-based DataLend – which tracks securities lending and borrowing activity – said its Target 50 Index is up from 57 points last month to 77 this week.

“The uptick is not “abnormal" per se, but we view this as a significant movement in our index,” DataLend director Chris Benedict told Global Investor/ISF.

Set-up last year, the gauge serves as a benchmark to determine how the hottest securities in the finance market are trending over time.

The list of the most expensive equities to borrow is  calculated by volume-weighted average fee/rebate rate and utilisation

“We are seeing our lender-to-broker on-loan balances increase from just below $1.7trn in early February to $1.84trn today," adds Benedict.

“Fees to borrow global assets have also increased from 44 bps to almost 49 bps during the same timeframe.”

These two factors, he says, are directly contributing to the increase in the DL50 index.

The highest recording to date for the index was 87 in April 2015.