Volatility-linked ETFs that track VIX futures contracts were down sharply for the fourth straight session Tuesday as fear drains from the market after the Greek elections.

iPath S&P 500 VIX Short-Term Futures ETN (NYSEArca: VXX) fell nearly 4% in early U.S. trading Tuesday.

The exchange traded note is down more than 20% from its June 13 closing price.

The ETN follows CBOE Volatility Index futures, not the spot price. The VIX is known as Wall Street’s “fear gauge” because it rises when investors are seeking protection in the options market.

VXX has a market cap of $1.5 billion, according to issuer Barclays. [VIX ETFs Thrive on Volatility and Risk Aversion]

Like all exchange traded products designed to track futures contracts, VXX can be hurt by “contango” in the futures market. [Caveat Emptor – Volatility ETFs]