Never before have US equity markets been so accessible – or so crowded. Twenty years ago, around 4 billion shares were traded daily across US stock markets. Today, it’s over 15 billion. Yet long-term investment managers like Orbis, Baillie Gifford, and Dodge & Cox account for only a fraction of that activity, and their share is shrinking.

The halfway point of any year is a good time to pause, reflect, and learn from what we’ve experienced. As we’ve often reminded you, studying the lessons from market history is essential preparation for future challenges.

"Doing something costs something. Doing nothing also costs something. And, quite often, doing nothing costs a whole lot more than doing...