An interest rate is simply the price of having money now instead of later. Because every asset is a claim on money that arrives later, that one price reaches into the value of practically everything.
At bottom, an interest rate is the price of time. It's what has to be paid to have money now instead of later, and, looked at the other way, what you get compensated for when you hand over money now in exchange for having it later. That sounds abstract. Its consequences are anything but, because almost every asset an investor might own is a claim on money that shows up sometime in the future.
The connection runs through something called discounting, and it's worth actually understanding rather than just nodding along. A sum arriving in ten years is worth less than the same sum arriving today, because today's money could be invested and would grow in the meantime. How much less depends entirely on the rate at which money can grow, the interest rate, in other words. When rates are high, a distant sum is worth a lot less today. When rates are low, it's worth much more.
Now think about what a share of a company actually is: a claim on the profits that business will generate over the rest of its life, which stretches many years into the future. The value of that claim today is the value of all those future profits, discounted back to the present. Raise the rate used to discount them, and the value of the claim falls, without a single thing changing about the underlying business. The company earns the same amount, sells the same amount, employs the same people. Only the price of time has moved.
This is how a decision made by a central bank, with no direct link to any one company, can move the price of every company at once. The rate goes up, the discount applied to future profits goes up, and the present value of every stream of future profits comes down. No corporate news required. The repricing is pure arithmetic, and it applies to bonds, property, shares, and any other claim on money that hasn't arrived yet.
The effect isn't uniform, and the shape of its unevenness explains a lot that otherwise looks baffling. A company whose profits mostly arrive soon is barely touched, because near-term money only gets discounted a little. A company whose value depends on big profits arriving many years out, which describes most fast-growing businesses, gets hit hard, because distant money is discounted heavily, and a change in the discount rate compounds across all those intervening years.
That's why rising rates tend to hurt growth-oriented companies far more than established, profitable ones, and it has nothing to do with judging the businesses themselves. It's purely mechanical. A growth company's value sits mostly in the distant future, and the distant future is exactly where a change in rates does the most damage. An investor who watches such companies fall hard when rates rise and concludes something broke in the business has confused an arithmetic consequence for a commercial one.
Rates also work through a second channel, entirely separate from discounting, and both run simultaneously. When rates rise, safe alternatives get more attractive. An investor who can earn a decent return on a government bond, at far less risk, needs a correspondingly better story from equities to justify holding them instead. Capital shifts around, and that shift itself moves prices. When rates sit very low, the safe alternatives pay almost nothing, and investors get pushed toward riskier assets just to find any return at all.
A third channel runs through the businesses themselves rather than through arithmetic. Companies borrow money, and when rates rise, their borrowing costs go up, which cuts into profits directly. Companies carrying a lot of debt feel this far more than companies carrying little, and a business that depends on continuously refinancing itself may find that a change in rates threatens its survival, not just its earnings. That's a real operational effect, distinct from the valuation effect that runs through discounting.
It's worth being clear about what this understanding doesn't give you, since the temptation to overreach here is considerable. Knowing that rates affect asset prices doesn't let an investor predict what rates will do next, and the track record of forecasting rates is poor even among people whose full-time job it is. An investor who understands the mechanism and then uses it to bet on where rates are headed has left the territory of understanding and wandered into the territory of prediction.
What the understanding does provide is an explanation, and that's genuinely valuable on its own. An investor watching their holdings fall while nothing has changed about the businesses they own is much better equipped for that moment if they know the price of time has moved, and that what they're seeing is an arithmetic revaluation, not a verdict on their judgment. An explanation isn't a prediction. But an explanation is exactly what lets an investor sit still instead of doing something rash.
One caution about the direction of causation, since this relationship gets described too simply far too often. Rates don't move for no reason. Central banks adjust them in response to economic conditions, raising them, typically, when inflation is a worry, and lowering them when growth is weakening. That means a change in rates always arrives with company: whatever conditions prompted the change come along with their own separate effects on businesses and markets. An investor watching prices fall as rates rise is seeing the discounting effect, but they may also be seeing the market's read on whatever economic conditions triggered the rate move in the first place, and the two are tangled together in ways that resist clean separation. The mechanism described here is real, and it is not the whole story. Treating it as the whole story would just trade one oversimplification for another.
VESTFY™ presents interest rates as the single most important concept linking the wider economy to the value of what an investor actually owns. Nearly every macroeconomic development that matters to markets matters through this channel, and an investor who understands discounting has picked up the key that makes a great deal of otherwise bewildering market behavior make sense.