Apple has had a rough few months. From October 2018 to January 2019, Apple’s market capitalization declined by more than the total market cap of Mexico or Saudi Arabia, falling by over $450bn in just a few months. That’s a one-company loss which is larger than the entire value of these national indices.
The chart below shows that for several years, growth stocks strongly outperformed value stocks. In plain terms, that means that already expensive stocks got very expensive, and already very expensive stocks then went on to get very, very expensive.