Individual companies don't trade in a vacuum — they float on a tide of inflation and interest rates. Understanding that tide explains why whole markets can rise or fall together regardless of any single company's results.
Inflation: the silent tax
Inflation measures how fast prices rise. At 3% a year, something costing $100 today costs $103 next year — and cash sitting idle quietly loses purchasing power. A key reason to invest at all is to grow your money faster than inflation erodes it.
Interest rates: the economy's thermostat
Central banks raise interest rates to cool an overheating, high-inflation economy and cut them to stimulate a weak one. Rates ripple everywhere: borrowing costs, mortgage payments, and crucially, what investments are worth.
| When rates rise | When rates fall |
|---|---|
| Borrowing gets pricier; growth slows | Borrowing gets cheaper; activity picks up |
| Bonds/savings pay more — competition for stocks | Bonds/savings pay less — stocks look relatively better |
| Stock valuations tend to compress | Stock valuations tend to expand |
Why higher rates push stock prices down
A stock is worth the company's future cash flows, valued in today's money. To compare future dollars to today's, we discount them — and the interest rate is the discount rate. Higher rates mean future profits are worth less today.
Why growth stocks fall most: a fast-growing company's biggest profits are expected years from now. The further out a payoff sits, the harder a higher discount rate shrinks its present value — so when rates jump, richly-valued growth names usually drop more than steady, profitable ones.
What it means for you
- Don't try to trade the macro. Rate moves are notoriously hard to predict; even the experts disagree.
- Expect valuations to breathe. The same company can command a higher or lower P/E purely because rates changed.
- Favour resilience. Businesses with pricing power and low debt weather inflation and higher rates far better.
- Diversify across assets. Bonds and stocks respond differently to rates — another reason for a thought-out asset allocation.
Takeaway: inflation erodes money and interest rates are the tool to fight it — and that single lever quietly sets the backdrop for every valuation. You can't control it, but understanding it explains a lot of what markets do.
