There's a silver lining in the stock market's tumble Thursday, the high-yield bond trackers are outperforming the S&P 500 SPX, -1.14% by a wide margin, which suggests the selling isn't being driven by fears of a liquidity squeeze. The SPDR Bloomberg Barclays High Yield Bond exchange-traded fund JNK, -0.29% slipped just 0.33% and the iShares iBoxx $ High Yield Corporate Bond ETF HYG, -0.23% eased just 0.27%, while the S&P 500 tumbled 1.43%. That's good news, because Wall Street traders would always prefer to sell because they want to, even if they are worried about a potential economic slowdown or a trade war, rather than being forced to sell to raise funds as market liquidity dries up.