Millionaire Librarian

There are several mental models of money that help us understand concepts that might not be immediately apparent.

One popular and particularly insightful model is the “money snowball.” When you first build a snowball, you pack the snow with your hands. It is cold, uncomfortable, and you are doing the majority of the work. However, after some time, the snowball gains enough heft that each rotation picks up more snow than the ball initially contained. Eventually, you reach the top of a metaphorical hill where gravity takes control, pulling the massive snowball down and gathering more and more snow on its own.

In this model, the snow represents your money, and the “invisible power” grabbing increasingly more snow with each turn represents your investment returns. At a certain point, there is little benefit to manually packing more snow or making individual contributions; you simply let gravity do the work. While small sacrifices matter significantly at the beginning, they become much less impactful later on.

This concept illustrates why starting early is so critical. If each turn of the snowball represents one year, a person starting ten years late is at a severe disadvantage. They aren’t just linearly smaller; they are exponentially smaller, as each additional turn picks up a volume of snow proportional to the snowball’s existing size.

To maximize this effect, you must keep all your “snow”—or investments—working for you as long as possible. Scraping off snow or failing to reinvest your returns will hinder the ultimate size of your wealth, especially in the early stages.

This is often explained by the 8-4-3 rule of investing:

• The first 8 years are slow; you are adding the majority of the snow yourself.
• The next 4 years, the momentum becomes noticeable as returns from your earlier gains start to contribute significantly to total growth.
• In the final 3 years, the “snowball effect” takes full control. The gains in these last three years can rival or even exceed the total growth of the previous 12 years combined.