Learn about GDP, inflation, and CPI - WPI

Overview

Gross Domestic Product (GDP), inflation, and price indices (CPI/WPI) are the fundamental macroeconomic indicators that drive stock market valuations, central bank policy, and sector rotation. Understanding these isn't optional—every earnings call, monetary policy decision, and valuation multiple depends on them.

GDP: The Economy's Report Card

Why GDP Matters to Investors

THREE critical transmission channels:

1. Corporate Earnings Growth: GDP growth ≈ revenue growth for most companies. If the economy grows5%, aggregate corporate revenues typically grow 4-6%.
2. Interest Rates: Central banks raise rates when GDP grows too fast (overheating risk), which reduces stock valuations (higher discount rates). They cut rates when GDP slows, boosting stocks.
3. Sector Rotation: High GDP growth → cyclicals outperform (autos, banks, real estate). Low GDP growth → defensives outperform (pharma, FMCG, utilities).

The Three Ways to Calculate GDP

WHERE:

• $C$ = Consumption (household spending: 55-60% of India's GDP)
• $I$ = Investment (business capex + residential construction: ~30%)
• $G$ = Government spending (infrastructure, salaries: ~12%)
• $X - M$ = Net exports (exports minus imports: often negative for India)

WHY this formula? Because GDP measures total spending on final goods. Every product sold is bought by one of these four groups.

Calculate nominal GDP:

$\text{GDP} = 150 + 70 + 30 + (50 - 60) = 150 + 70 + 30 - 10 = ₹240 \text{ trillion}$

Why this step? We add all domestic spending, then subtract imports because imports are foreign production (they're in $C, I, G$ but shouldn't count in our GDP).

Nominal vs Real GDP

$\text{Real GDP} = \frac{\text{Nominal GDP}}{\text{GDP Deflator}} \times 100$

WHY the distinction matters: If nominal GDP grows 10% but inflation is 8%, the economy only really grew 2%. Stock investors care about real growth because only real growth increases actual production capacity and long-term earnings power.

Real GDP in Year 2:

$\text{Real GDP}_2 = \frac{220}{108} \times 100 = 203.7 \text{ trillion}$

Real GDP growth rate:

$\text{Growth} = \frac{203.7 - 200}{200} \times 100\% = 1.85\%$

Why this step? Dividing by the deflator removes price increases, leaving only quantity increases. The economy grew 10% nominally but only 1.85% in real terms—inflation ate8.15%.

Inflation: The Silent Wealth Destroyer

Why Inflation Destroys AND Creates

Two faces of inflation for investors:

1. Earnings Impact: Moderate inflation (3-5%) lets companies raise prices → higher nominal earnings → stocks rise. But high inflation (>7%) increases input costs faster than pricing power allows → margin compression.
2. Valuation Impact: Inflation forces central banks to raise interest rates → higher discount for future cash flows → lower P/E multiples. The formula: Stock Value = Earnings / (Discount Rate). If discount rate ↑, value ↓.

The Inflation-Interest Rate-Stock Valuation Chain

Simplified (for small rates): $\text{Nominal Rate} \approx \text{Real Rate} + \text{Inflation Rate}$

WHY this matters: If inflation is 6% and you need a 3% real return, you demand 9% nominal return. When inflation rises, required returns rise → stock prices fall (present value drops).

Stock valuation impact (simplified): A stock earning ₹10/year, valued at:

• Year 1: ₹10 / 0.05 = ₹200
• Year 2: ₹10 / 0.10 = ₹100

Why this step? Higher discount rate divides earnings by a bigger number → lower present value. This is why stocks crash when inflation surges unexpectedly.

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## CPI: The Consumer's Inflation Gauge

### How CPI is Constructed

STEP-BY-STEP:

1. Select a basket: Survey thousands of households to find what they buy (e.g., rice, rent, fuel, clothes).

2. Assign weights: Food might be 45% of spending, housing 15%, transport 10%, etc.

3. Collect prices: Every month, surveyors record prices at thousands of retail locations.

4. Calculate index: Base year = 100. If prices rise 5%, index = 105.

$\text{CPI} = \frac{\sum (\text{Current Price}_i \times \text{Quantity}_i)}{\sum (\text{Base Price}_i \times \text{Quantity}_i)} \times 100$

Inflation rate: \text{Inflation} = \frac{\text{CPI}_{\text{current}} - \text{CPI}_{\text{previous}}}{\text{CPI}_{\text{previous}} \times 100\%

WHY this formula? It's a Laspeyres index—quantities fixed at base-year levels, so only price changes matter. This isolates pure inflation from consumption shifts.

Base year cost: $10 \times 40 + 2 \times 200 + 1 \times 100 = 400 + 400 + 100 = ₹900$

Current year cost: $10 \times 45 + 2 \times 250 + 1 \times 110 = 450 + 500 + 110 = ₹1060$

CPI (base = 100): $\text{CPI} = \frac{1060}{900} \times 100 = 117.8$

Inflation: $\text{Inflation} = \frac{117.8 - 100}{100} \times 100\% = 17.8\%$

Why this step? We compare the cost of the same basket at different times. If the basket costs 17.8% more, that's the inflation rate consumers experience.

CPI vs Core CPI

Example: If overall CPI = 6% but core CPI = 3%, the RBI knows 3% is from oil shocks (temporary) and won't hike rates agressively.

WPI: The Wholesale Inflation Signal

WPI vs CPI: Key Differences

WHY WPI matters: If WPI rises sharply, companies face input cost pressure → either margins shrink (bad for stocks) or they raise prices (CPI rises → RBI hikes rates → stocks fall). WPI is a canary in the coal mine.

Why this lag? Wholesale costs → production costs → retail prices. Smart investors watch WPI trends to forecast CPI moves before the market reacts.

The Macro-to-Micro Investing Playbook

SCENARIO 1: High GDP Growth (7%+), Low Inflation (3-4%)

• What happens: Strong earnings growth, no rate hike pressure
• Winners: Cyclicals (banks, autos, capital goods, real estate)
• Losers: Defensives underperform (boring but stable)

SCENARIO 2: High GDP Growth (7%+), High Inflation (6%+)

• What happens: RBI hikes rates → borrowing costs rise → valuations compress
• Winners: Companies with pricing power (FMCG brands, pharma)
• Losers: Highly leveraged sectors (real estate, NBFCs)

SCENARIO 3: Low GDP Growth (3-4%), High Inflation (stagflation)

• What happens: Worst case—earnings fall, rates stay high
• Winners: Gold, defensives (utilities, pharma)
• Losers: Almost everything; cash is king

SCENARIO 4: Low GDP Growth (3-4%), Low Inflation (2-3%)

• What happens: Rate cuts likely, slow recovery
• Winners: Interest-ratesensitive (IT exports benefit from weak rupee, banks on rate cuts)
• Losers: Commodity producers

Why it's wrong: If GDP grows 10% but inflation is 9%, real growth is only 1%—markets will fall because high inflation forces rate hikes, which crush valuations. Also, if GDP growth is entirely from government spending (not productive investment), corporate profits may not rise.

The fix: Check real GDP growth and the composition (consumption-led? investment-led?). Investment-led growth is more sustainable for stocks.

Why it's wrong: For businesses, WPI matters more for input costs. A steel companyares about iron ore WPI, not food CPI. Also, asset inflation (real estate, stocks) isn't in CPI but affects wealth and spending.

The fix: Track WPI for cost pressures, CPI for demand and policy, and asset prices for wealth effects. Use all three.

But wait—sugar prices doubled! So even though you earned ₹550, you can only buy half the sugar you could before. Your real growth is way less than 10% because inflation (sugar getting expensive) ate your gains.

CPI is like tracking the price of YOUR favorite snacks (chips, candy, lemonade) every week. If they all cost 5% more, your pocket money buys 5% less—that's inflation for you.

WPI is like tracking the price youremonade stand pays for sugar and lemons (wholesale). If those go up, you either make less profit or raise your lemonade price, which makes CPI go up later!

So: GDP = size of economy. Inflation = how fast prices rise. CPI = what you pay at the store. WPI = what businesses pay before stuff reaches stores.

For inflation winners: "Price Power Protects Profits" → Companies with pricing power survive inflation.

Connections

• Understanding Economic Cycles and Sector Rotation – GDP/inflation define cycle phases
• Central Bank Monetary Policy and Interest Rates – RBI uses CPI target (4% ±2%) to set rates
• Discounted Cash Flow (DCF) Valuation – Inflation affects discount rates → stock valuations
• FMCG Stocks and Pricing Power – High CPI inflation tests brand pricing power
• Real vs Nominal Returns – Always deflate by CPI to find real gains
• Bond Yields and Inflation Expectations – 10Y bond yield = real rate + inflation expectations
• Currency and Exports – High inflation → currency depreciates → export competitiveness rises

#flashcards/stock-market

What does GDP measure? :: The total market value of all final goods and services produced within a country's borders in a specific time period.

Write the GDP expenditure formula :: GDP = C + I + G + (X - M), where C = Consumption, I = Investment, G = Government spending, X = Exports, M = Imports

Concept Map

Hinglish (regional understanding)