Understand interest rates and central bank policy — Stock-Market notes

Overview

Interest rates are the cost of borrowing money, and central banks (like the Federal Reserve, ECB, RBI) control them to manage economic growth and inflation. For investors, interest rates are the invisible hand that moves stock valuations—they determine how much future earnings are worth today and where capital flows (stocks vs bonds vs savings).

Why this matters for stock investing: When rates rise, stocks (especially growth stocks) become less attractive because:

Future cash flows are discounted more heavily (lower present value)
Bonds become competitive alternatives
Borrowing costs increase for companies, squeezing profits

Figure — Understand interest rates and central bank policy

Core Concepts

How Interest Rates Work: First Principles

The Time Value of Money

WHY do interest rates exist? Money today is worth more than money tomorrow because:

Opportunity cost: You could invest it and earn returns
Inflation: Money loses purchasing power over time
Risk: Uncertainty the borrower might default

Derivation of present value:

Start with the fundamental question: What is $1 received in the future worth today?

If I can earn rate $r$ period, then:

$1 today becomes$ (1 + r)$ in one period
Therefore, to have $1 in one period, I need$ \frac{1}{1+r}$ today

For money received in $n$ periods:

$\text{Present Value} = \frac{\text{Future Value}}{(1 + r)^n}$

WHY this exponent? Each period compounds the discount. After2 periods:

First period: $\frac{1}{1+r}$
Second period: $\frac{1}{1+r} \times \frac{1}{1+r} = \frac{1}{(1+r)^2}$

Central Bank Policy Tools

1. Setting the Policy Rate

HOW it works: Central banks set a target rate (Fed Funds Rate, Repo Rate, etc.). Banks use this as a baseline for all lending.

Transmission mechanism:

Central bank raises target rate
Banks raise rates on loans, mortgages, credit cards
Borrowing becomes expensive → less spending
Demand falls → inflation cools

WHY this chain? Each link is about incentives. Higher rates make saving more attractive than spending/investing.

2. Open Market Operations

WHAT: Central bank buys or sells government bonds.

HOW buying lowers rates:

Central bank buys bonds from banks
Banks now have more cash reserves
More supply of lendable money → rates fall
Banks compete for borrowers, lowering rates further

WHY selling raises rates: Reverse process—drains cash from system, less to lend, rates rise.

3. Forward Guidance

WHAT: Central bank signals future policy intentions.

WHY it works: Markets price assets based on expected future rates. If Fed says "rates staying low through 2024," investors pour into long-duration assets now.

Danger: If central bank loses credibility (promises low rates but then spikes them), market crashes (see 2022).

The Rate-Stock Relationship

Formula Equity Risk Premium

$\text{Expected Stock Return} = \text{Risk-Free Rate} + \text{Equity Risk Premium}$

Where:

Risk-free rate ≈ 10-year Treasury yield (linked to central bank policy)
Equity risk premium = Extra return demanded for stock risk (usually 4-6%)

Derivation from investor behavior:

Investor wants return $r_e$ from stocks
Can get $r_f$ risk-free from bonds
Will only buy stocks if $r_e \geq r_f + \text{premium for risk}$

WHY this matters: When $r_f$ rises (Fed hikes), stocks must offer higher expected returns to compete. Higher expected return = lower valuation today (prices fall).

Worked example 2022 Rate Hikes Crush Growth Stocks

Setup: Fed raises rates from 0% to 5% in 18 months to fight9% inflation.

Company: High-growth SaaS company trading at 40x sales, no profits, expecting growth in years 5-10.

At 0% rates: $V_0 = \frac{1000}{(1.06)^7} = \$665 \text{ (using 6\% discount: 0\% risk-free + 6\% equity premium)}$ At 5% rates: $V_0 = \frac{1000}{(1.11)^7} = \$481 \text{ (using 11\% discount: 5\% risk-free + 6\% equity premium)}$

WHY this calculation? Same future cash flow, but higher discount rate from rising risk-free rate.

Result: 28% valuation drop from rates alone. Nasdaq fell 33% in 2022—this math explains it.

Inflation Targeting

WHAT: Most central banks target 2% annual inflation.

WHY 2%?

Not 0%: Risk of deflation (prices falling → people delay purchases → economic spiral)
Not 5%+: Erodes purchasing power, creates uncertainty
2% sweet spot: Enough buffer above deflation, low enough to preserve value

HOW central banks control inflation:

Taylor Rule (simplified policy guideline):

$i_t = r^* + \pi_t + 0.5(\pi_t - \pi^*) + 0.5(y_t - y^*)$

Where:

$i_t$ = Target interest rate
$r^*$ = Neutral real rate (~2%)
$\pi_t$ = Current inflation
$\pi^*$ = Target inflation (2%)
$y_t - y^*$ = Output gap (actual GDP vs potential)

WHY these coefficients (0.5)? Empirically derived—aggressive enough to control inflation without causing recessions.

Policy Lag Times

Critical insight: Monetary policy works with 6-18 month delays.

WHY?

Decision lag: Central bank meets every 6-8 weeks, needs data to confirm trends
Transmission lag: Rate changes take months to affect borrowing behavior
Effect lag: Spending/investment changes take quarters to hit GDP/inflation

Investor implication: By the time Fed cuts rates, recession might already be here. By the time they hike, inflation might have peaked. Market tries to front-run these moves.

Rate Cycles and Sector Rotation

Different sectors react differently to rate changes:

Rate-sensitive (hurt by hikes):

Growth tech: Valued on distant cash flows (high duration)
Real estate (REITs): Compete with bonds for income, rising mortgage rates hurt
Utilities: High debt loads, income investors flee to bonds

Rate-beneficiaries (helped by hikes):

Banks: Earn more on loans than pay on deposits (widening spread)
Insurers: Invest premiums at higher yields
Value stocks: Near-term earnings matter more, less discounting impact

International Considerations

Currency impact: Higher rates attract foreign capital → currency strengthens.

Example: If Fed raises to 5% while ECB stays at 2%, investors buy dollars to invest US bonds → dollar strengthens → US exports become expensive → hurts US multinationals (Apple, Microsoft).

Emerging markets: Especially vulnerable. If Fed raises rates, capital flees EM → currency crashes → imported inflation → EM central banks forced to raise rates too → recession.

Investor takeaway: Fed policy affects global stocks, not just US.

Recall Feynman: Explain to a 12-Year-Old

Imagine you have a lemonade stand. Interest rates are like the "rental fee" for money.

When the neighborhood council (central bank) makes borrowing expensive (high rates), fewer people borrow to start lemonade stands. Less competition, but also fewer customers because everyone's saving money instead of spending. Your lemonade stand's future profits are worth less today because you could put money in the bank and earn a lot just waiting.

When they make borrowing cheap (low rates), everyone borows to start stands (more competition), but also more people have money to spend on lemonade. Your stand's future profits are worth MORE today because banks pay almost nothing—better to own the stand.

The council raises/lowers this rental fee to keep the neighborhood economy balanced: not too hot (everyone buying everything, prices skyrocket), not too cold (nobody buying, stands close down).

Connections Time Value of Money - Foundation for understanding rate impact

Discounted Cash Flow (DCF) Valuation - How to calculate intrinsic value with rates
Bond Yields and Stock Competition - Alternative investment relationship
Inflation Dynamics - Why central banks adjust rates
Sector Rotation Strategies - Positioning for rate cycles
Growth vs Value Stocks - Different sensitivities to rates
Financial Sector Analysis - Banks benefit from rate hikes
Tech Stock Valuation - Long-duration assets most rate-sensitive
Currency Exchange Rates - International rate differentials
Economic Indicators - Data central banks watch (CPI, PCE, unemployment)
Yield Curve Analysis - Market's rate expectations
Recession Indicators - Inverted curve, Fed tightening cycles

#flashcards/stock-market

What is the interest rate? :: The cost of borrowing money or return on lending/saving, expressed as a percentage, typically annualized. Represents time value of money plus risk.

What is a central bank's primary role?

Control monetary policy by setting interest rates and managing money supply to achieve economic stability, typically targeting ~2% inflation and full employment.

How does raising interest rates slow inflation?

Makes borrowing expensive → reduces spending and investment → lowers demand → prices stop rising as fast. Transmission takes 6-18 months.

What is quantitative easing (QE)?

Central bank buys government bonds to inject money into the economy, increasing bank reserves and lowering long-term interest rates.

Why do growth stocks fall more than value stocks when rates rise?

Growth stocks are valued on distant future earnings. Higher discount rates reduce present value more for cash flows far in the future (longer duration).

What is the equity risk premium?

The extra return investors demand for taking stock risk over-free bonds. Typically 4-6%. Formula: Expected stock return = Risk-free rate + Equity risk premium.

Why do banks benefit from higher interest rates?

They earn more on loans than they pay on deposits (net interest margin expands). Example: lend at 7%, pay depositors 0.5% = 6.5% spread.

What is the Taylor Rule?

A guideline for setting interest rates based on inflation deviation from target and output gap. Formula: i = r* + π + 0.5(π - π*) + 0.5(output gap).

Why do central banks target 2% inflation instead of 0%?

Provides buffer above deflation (which causes economic spirals), while being low enough to preserve purchasing power and maintain stable expectations.

What is forward guidance?

Central bank communication about future policy intentions to influence market expectations and behavior today. Works because markets price based on expected future rates.

How do interest rates affect currency values?

Higher rates attract foreign capital seeking returns → increased demand for currency → currency strengthens → exports become more expensive.

What is the policy lag time for monetary policy?

6-18 months total. Decision lag (weeks), transmission lag (months for behavior change), effect lag (quarters for economic impact).

Why might a company's stock fall even if rates drop?

If rate cuts signal recession, earnings expectations fall faster than discount rate benefit. Market may have already priced in cuts. Broader economic damage may overwhelm rate benefit.

What sectors benefit most from rising rates?

Financials (banks, insurers - earn more on assets), value stocks (less sensitive to discounting), and sometimes energy (often correlates with inflation/growth that prompts hikes).

What is quantitative tightening (QT)? :: Central bank sells bonds or lets them mature without replacement, draining money from the system and raising long-term rates. Opposite of QE.

How does present value formula explain stock market crashes during rate hikes?

PV = Future Value / (1+r)^n. As r increases, denominator grows exponentially for distant cash flows, crushing valuations of growth stocks with far-out profitability.

Concept Map

Hinglish (regional understanding)

Intuition Hinglish mein samjho

Interest rates aur central bank policy ko samajhna stock market ke liye bahut zaroori hai kyunki yeh directly apke investments ki value ko affect karta hai. Socho ki interest ratek thermostat ki tarah hai—economy ko control karta hai. Jab inflation zyada ho jata hai (prices too fast badhte hain), toh central bank (jaise Federal Reserve ya RBI) interest rates badha deta hai taki borrowing expensive ho jaye. Expensive borrowing ka matlab hai kam spending, kam investment, aur eventually prices stabilize ho jate hain. Opposite mein, jab economy slow hai aur recession ka dar hai, toh rates ko gira dete hain taki log zyada borrow karein, spend karein, aur economy chale.

Investors ke liye yeh isliye matter karta hai: jab rates high hote hain, toh bonds attractive ho jate hain (safe returns mil rahe hain), aur log stocks se paise nikaal ke bonds mein daal dete hain. Plus, higher discount rate ka matlab hai ki future earnings ka present value kam ho jata hai—especially growth stocks ke liye jo profits5-10 saal bad expect karte hain. Formula simple hai: PV = Future Value / (1 + r)^n. Jitna bada 'r' (interest rate), utna chota present value. Isliye 2022 mein jab Fed ne rates0% se 5% tak badha diye, tech stocks crash ho gaye—unki distant future earnings ab bahut kam worth kar rahi thi.

Yeh samajhna important hai ki different sectors differently react karte hain. Banks aur financials ko higher rates pasand hain kyunki woh loans pezyada earn karte hain. Lekin real estate aur growth tech hurtote hain kyunki unki valuations future cash flows pe dependent hain. Ek smart investor rate cycles ko track karta hai aur accordingly apna portfolio adjust karta hai—rates badh rahe hain toh value stocks aur financials mein shift karo, rates gir rahe hain toh growth stocks mein wapas ao.

Yad rakho ki central bank policy mein lag time hota hai—6 se 18 months. Matlab jab Fed rate hike karta hai, uska actual economic impact mahino bad dikhta hai. Isliye markets "forward-looking" hote hain—woh try karte hain anticipate karne ki Fed next kya karega, aur accordingly prices adjust ho jati hain pehle hi. Agar ap yeh dynamics samajh gaye, toh ap better decisions le sakte ho kiab kaunse stocks buy karne hain aur kab cash mein rehna hai. Central bank ki policy announcements, inflation data (CPI, PCE), aur economic indicators (unemployment, GDP growth) ko closely follow karna seekho—yeh sab signals dete hain ki rates kahan ja rahe hain aur apka portfolio kaise adjust karna chahiye.

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