The Half-Life of What We Know

Much of what we know is quietly expiring.

Not all at once, but steadily, like all knowledge over time, a little less current each year, a little further from the world it was learned in.

The process we mastered, the system we knew inside out, the judgment we honed over a decade of mistakes and successes — all of it losing its edge. It all has a half-life, and that half-life is getting shorter.

The World Economic Forum's Future of Jobs Report 2025 puts a number to the shift: employers expect 39% of workers' core skills to change by 2030, nearly two in five, in the space of a single strategy cycle.

Not all of it fades at the same rate, of course. The specific expires fastest : this tool, this procedure, this version of the rule. Judgment lasts far longer. But even judgment stays sharp only while it keeps meeting new situations; left alone, the surest expertise quietly drifts out of date too.

The deepest things: how to listen, how to earn trust, how to weigh a hard decision, the principles beneath a craft outlast every tool and every rule. But these are the hardest of all to write down. You cannot capture how to read a room in a procedure. So the knowledge that lasts longest is the knowledge most dependent on being passed from one person to another. What endures and what must be shared turn out to be the same thing.

It is the working reality of every knowledge worker right now.

Here is what makes it harder.

The moment knowledge is written down is the moment its half-life begins.

Not because writing it down is wrong. We need the record — the document, the process map, the carefully captured procedure. But a document freezes knowledge at the instant of its writing. It captures what was true that moment. It cannot capture what changed the day after, or the quiet exception everyone learned about later, or the reason the rule existed in the first place.

The page does not age with the world. The world moves on, and the page stays where it was.

Which is why so much of what an organisation actually relies on never makes it onto a page at all. It sits with people in their judgment, their instinct, their memory of why things are the way they are.

That knowledge lives in people, and when we cannot reach it, the cost is quiet but continuous — hours lost to hunting for information, chasing updates, and reconstructing what someone else already knew, instead of doing the work we were actually hired for.

The most experienced person in the room is often the one quietly correcting what the document says. They are holding the part the record could never hold.

So if everything we know is slowly expiring, what keeps any of it alive?

The answer is older than every system we have ever built — it's conversation.

The smallest unit of living knowledge is not the document or the database. It is the moment two people exchange something — one who carries it, one who needs it and both walk away slightly changed.

Knowledge that stays in motion does not decay the same way. It gets questioned, updated, and retold in light of something new. Every time it passes between two people, the clock resets a little.

Think about how we actually learned the things we know best.

Not from the manual, but from the colleague who explained what the manual missed. From the question we asked that opened something. From the ten-minute conversation that taught us more than the forty-page guide.

None of this means the page has no power. Its permanence is exactly its strength: a document does not change in the retelling, does not forget, does not favour the loudest voice in the room and it can be checked. Conversation can do all of those things, and sometimes badly. So the point was never to choose one over the other. It is the handoff between them — the living word and the lasting record — that keeps knowledge both current and trustworthy. The page holds it still; the conversation keeps it moving.

The encouraging part is that the data points the same way.

That WEF figure of 39% is down from 44% just two years earlier. The Forum attributes the slowdown not to better software, but to organisations investing more intentionally in continuous learning, reskilling, and the transfer of knowledge between people.

In other words, decay slows where knowledge continues to move.

This is why the enduring practices are the human ones and the most useful of them are simple.

Schedule the handover conversation before someone leaves, not after. By the time a resignation is processed, the calendar fills with everything except the one exchange that matters most, the unhurried sit-down where years of judgment can actually pass from one person to another. The knowledge most worth keeping is rarely written down in the final two weeks. It is spoken, if we make the room for it.

Pair the person who carries the knowledge with the person who needs it intentionally. Mentoring, communities of practice, shadowing — all the same quiet act: two people, one carrying something, one reaching for it. They work for the same old reason: they pass the flame from one hand to the next.

If expertise fades, hoarding it makes no sense. The knowledge we guard most closely is often the knowledge ageing fastest — left untouched, untested, and quietly becoming outdated.

But the knowledge we share continues to thrive. Every time we explain something, mentor someone, or answer the underlying question, we do not deplete what we know, we reset its clock, and theirs too.

And it is not JUST the act of giving that keeps the flame alive. A GOOD QUESTION can be just as valuable as a generous answer; the person who asks well keeps knowledge moving as surely as the one who shares.

So perhaps the goal was never to accumulate knowledge and protect it.

Perhaps it was always to keep it in motion.

What we know is not a vault to guard. It is a fire to keep lit and we keep it lit by passing it on to the next pair of waiting hands.

A note on scope: this piece is written from a knowledge management perspective, and it speaks to knowledge that is meant to be shared — the operational understanding, judgment, and experience an organisation depends on to function. It is not an argument for sharing everything. Plenty of knowledge should stay held: information that is confidential, proprietary, personal, or legally protected, and anything whose disclosure could harm a person, a relationship, or a reputation. Discretion is its own form of stewardship. The case here is narrower — that the knowledge we do intend to keep alive stays alive only when it keeps moving between people.

Reference:

World Economic Forum, Future of Jobs Report 2025 (January 2025). https://www.weforum.org/publications/the-future-of-jobs-report-2025/