Boston’s 1924 experiment in shared investing
Before a pooled fund, someone seeking a spread of investments had to choose and buy securities one by one—or rely on an intermediary to do it. In 1924, the Massachusetts Investors Trust in Boston offered another route: investors bought shares in a common portfolio, and professional managers selected and held the investments for the group.
That arrangement changed the unit of access. A buyer did not need to purchase a whole bond or build a broad portfolio alone; a share represented a portion of the fund’s combined holdings.
The feature that made the model expandable
The trust helped establish the modern open-end mutual fund. “Open-end” means the fund can issue new shares as people invest and redeem shares when they withdraw. That differs from a closed pool, whose shares generally change hands between investors rather than expanding or shrinking directly with demand.
When investors put money in, the fund can add it to the portfolio; when they leave, the fund can sell holdings to pay them. The share price is tied to the value of the underlying investments, so buyers participate in the same pool rather than bidding against one another for a fixed supply of shares.
A portfolio bought one share at a time
Pooling did not remove investment risk: the fund’s value could still rise or fall with its holdings. But it made diversification—the spreading of money across multiple investments—available through a single purchase. The lasting shift was practical: instead of assembling a portfolio security by security, an individual could buy into one.
