At its heart, portfolio management involves managing risk. Random shocks often occur, affecting groups of companies that share the same business risks. For example, Technology companies, which can be found in many different sectors, sharply sold off at the start of this week (10.4.21). The sell-off was led by Interactive Media & Services (-3.08%), Semiconductors (-2.76%), Software (-2.29%) and Hardware (-2.22%), while the market was down 1.30% and the average stock down only 0.63%. With technology companies spanning several sectors and trading as a thematic group, we question whether investors are aware of their total exposure to the technology theme.