A big reason why technology-heavy Nasdaq Composite          COMP,         -1.37%        is dropping 1.5% in afternoon trading Thursday while the Dow Jones Industrial Average         DJIA,         +0.91%        is rallying 292 points, or 0.9%, is the bad performance of the shares of the four biggest tech names. Of the four U.S. companies with market capitalizations of over $1 trillion, shares of Apple Inc.          AAPL,         -2.77%        dropped 3.1%, Microsoft Corp.          MSFT,         -1.57%        slid 1.9%, Alphabet Inc.          GOOGL,         -2.76%         GOOG,         -2.26%        sank 2.9% and Amazon.com Inc.          AMZN,         -4.12%        slid 4.1%. Based on the number of shares outstanding provided in the companies’ latest quarterly filings, the stock price declines are wiping out a total of about $191.3 billion in market capitalization. Keep in mind that the Nasdaq is a market-cap weighted index and the Dow is a price-weighted index. Of the Big 4 tech companies, only Apple and Microsoft are in the Dow. Microsoft’s stock is the 6th highest-priced Dow stock and Apple’s stock is 15th. Together, those stocks’ price drops are shaving about 60 points off the Dow’s price.