What it means
The rule is usually traced to a court decision in Massachusetts in 1830, often called the Harvard College case. The judge said a trustee must act with the care, skill and caution that sensible people use in managing their own affairs, with attention to the safety of the capital and the income it produces.
The wording was widely copied in later trust statutes in the United States and in other countries that follow the common law. In practice the old rule judged each investment on its own.
Some jurisdictions went further by publishing approved lists of safe holdings, which often meant government bonds and a short list of other conservative assets. Trustees who stayed on the list were treated as safe from challenge, whatever happened to the investment.
The weakness was that it discouraged diversification. A trustee who bought a risky but sensible mix of assets could be criticised because one holding looked speculative, even though the combined portfolio was balanced.
Critics argued that the rule protected trustees from blame more than it protected beneficiaries from loss. That led to reform.
Modern trust and pension laws in many places now use the prudent investor standard, which asks whether the portfolio as a whole suits the purpose and risk profile of the beneficiaries. The older wording is still seen in contracts, older trust deeds and some regulatory language.
For a business reader, the phrase signals a cautious, documented approach to other people's money. If a pension committee or trust company refers to the rule, it normally means the decision maker is expected to show care, avoid speculation and be able to explain every choice afterwards.
In practice
Real-world examples.
Example
A small-town trust company holds money for a retired teacher. Following an older trust deed that still uses the prudent man wording, it keeps the money in high-grade bonds and a savings account and avoids start-up shares, and its file notes record why. The trust company reviews the arrangement each year and checks whether the deed can be updated by agreement of the family.
Example
A charity board is asked by a donor to put a gift into a friend's new restaurant venture. The treasurer declines, explaining that a sensible person managing money for others would not place a large share of it in one unproven business.
Example
A law firm advising a family trust compares the deed's old wording with the modern prudent investor standard. It concludes that a diversified portfolio is now allowed, and it records this in a memo before the trustees change the mix. The memo is kept with the trust papers so future trustees can see why the approach changed.
Case study
Seen in the real world.
Eastgate Charitable Trust is an illustrative, fictional foundation whose founding document, written decades ago, required trustees to invest as a prudent man would. For years the trustees kept nearly everything in government bonds, and inflation slowly eroded the real value of the fund.
A new treasurer asked a lawyer whether the wording blocked a more balanced approach. The advice was that the modern standard in the trust's jurisdiction looked at the portfolio as a whole, so a diversified mix was allowed if it was documented.
The trustees agreed a policy with limits on each asset class and reviewed it annually. A summary of the policy was sent to the beneficiaries, who welcomed the clearer explanation of how their money was managed. They also asked the lawyer to update the wording of the deed at the next opportunity so the question would not return. The illustrative lesson is that old legal wording can hold a fund back unless someone checks how the law has changed.
Watch out
Common mistakes.
- Believing the rule bans all risk, when the original ruling asked for the care of a sensible person, not for the avoidance of every uncertain asset.
- Applying the rule to each investment separately and ignoring how a holding fits within a diversified portfolio.
- Assuming it is still the governing standard everywhere, when many jurisdictions have moved to the prudent investor approach.
Questions
People also ask.
Where did the prudent man rule come from?
It comes from a nineteenth century Massachusetts court decision, Harvard College v. Amory, and it spread through trust law in many countries.
Is the prudent man rule still in force?
In many places it has been replaced by the prudent investor standard, although the older wording still appears in some deeds and regulations. The safest course is to ask a lawyer which standard applies to the trust or fund in question.
Who is the prudent man in the rule?
The prudent man is a notional sensible person, and the test is whether the trustee acted as such a person would have acted with similar funds.
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