Even with the S&P 500 hitting new record highs on an almost daily basis, short sellers are not deterred and continue to load up on bearish bets on some of the largest exchange traded funds.

Nearly 11% of the shares outstanding in the SPDR S&P 500 ETF (NYSEArca: SPY), the world’s largest ETF by assets, are sold short, “the highest proportion since 2012,” Bloomberg reported citing internal data and data from Markit Securities.

Bearish bets on the PowerShares QQQ (NasdaqGM: QQQ), the NASDAQ-100 tracking ETF are 4.1% of shares outstanding, down from 5.9% last month, according to Bloomberg. The article also notes bearish wagers against an unidentified technology ETF have surged 67% above 12-month average.

The recent performance of U.S. equities shows the shorts are living dangerously. The S&P 500 is up almost 4% in the past month while QQQ is higher by nearly 7% over the same time. Assuming the unidentified tech ETF where bearish wagers are mounting is the Technology Select Sector SPDR (NYSEArca: XLK) or any of its rivals funds, traders are paying a heavy price to short those ETFs.

Buoyed by Apple’s (NasdaqGS: AAPL) resurgence and the sturdiness of a plethora of old school tech stocks even as Internet and social media names have struggled, XLK is up 8.2% year-to-date. [Old Tech, New Tech in One ETF]

Other sector and industry ETFs have high levels of short interest despite recently impressive performances. The iShares Nasdaq Biotechnology ETF (NasdaqGM: IBB) is up 9% in the past month while theSPDR S&P Biotech ETF (NYSEArca: XBI) is up 11.5% over the same time with the benefit of a 6.2% gain Monday.