--- title: "Inflation, Price Indexes and Real Values" description: "A simple price index compares a fixed basket's cost with its base-year cost, setting the base index to 100. Inflation is the percentage change in the index. Divide a nominal amount by (index / 100) to" canonical: https://lightmysky.com/learn/civics-and-economics/inflation-price-indexes-and-real-values-mt_58FeRqSjYh source: https://lightmysky.com/learn/civics-and-economics/inflation-price-indexes-and-real-values-mt_58FeRqSjYh.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Inflation, Price Indexes and Real Values A simple price index compares a fixed basket's cost with its base-year cost, setting the base index to 100. Inflation is the percentage change in the index. Divide a nominal amount by (index / 100) to express it in base-year money. Price adjustments help compare wages across years, while a household's spending may differ from the published index basket. Subject: Civics & Economics · Area: Economics · Ages 15 to 16 Page: https://lightmysky.com/learn/civics-and-economics/inflation-price-indexes-and-real-values-mt_58FeRqSjYh ## Ready when they can - Calculate a simple basket price index and the inflation rate between two years - Convert a wage from twenty years ago into today's money and say whether it rose in real terms - Name a reason the published index misses what a particular household actually feels ## Lesson: Reading prices across years fairly Inflation is a rise in the general price level. Some prices can fall while the overall level rises. Deflation is a fall in the general price level. Hyperinflation is an extreme, rapid rise in prices that quickly reduces money's buying power. One shop changing one price does not establish inflation across an economy. **Example.** For a simple index, keep basket quantities fixed. Multiply each price by its quantity, then add. Two rides at $3 each and one $4 sandwich cost $10. Later, rides cost $4 each and the sandwich still costs $4, so the basket costs $12. Index = current basket cost / base basket cost x 100. The later index is 12 / 10 x 100 = 120. Index numbers have no dollar or percent sign. *(drawing: The quantities stay fixed. The cost rises from $10 to $12, and the index rises from 100 to 120.)* Inflation rate = (new index - old index) / old index x 100. Use the old index as the denominator, even when it is not 100. If an index rises from 150 to 156, the increase is 6. Dividing 6 by 150 and multiplying by 100 gives 4 percent inflation, not 6 percent. Nominal pay is the money amount. Real pay adjusts for prices. With a base-100 index, real pay in base-year money = nominal pay / (index / 100). To compare percentage changes, calculate (1 + pay rise / 100) / (1 + inflation / 100). A ratio below 1 means buying power fell. Subtract 1 from the ratio and multiply by 100 to find the percentage change in buying power. **Example.** To express an old wage in current money, multiply it by current index / old index. Twenty years ago, an hourly wage was $10 at index 80. At today's index of 120, that wage equals $10 x 120 / 80 = $15 in today's money. A current wage of $16 buys more than that old wage, before tax. Unexpected inflation reduces the real value of loan payments fixed in money. The borrower repays less buying power than expected; the lender receives less. This does not guarantee an easier budget if the borrower's income fails to keep up. Savings lose buying power when their nominal return is below inflation. Deflation increases cash's buying power and the real value of payments fixed in money. A consumer price index represents its covered population's spending. A household spending more of its budget on rapidly rising rent can face faster bill increases. Spending shares give some prices more weight. A fixed basket can overstate the cost of maintaining a living standard when shoppers switch to cheaper alternatives. Official methods may adjust for this substitution. **Recap.** Calculate inflation from the old index. Adjust wages for prices before comparing buying power. A household's spending may differ from the index basket. *Lesson, questions, worked solutions and flashcards written for this dataset. OpenStax inflation material was consulted for facts and teaching structure.* ## Practice 8 questions on this page, each with its working shown. ## Optional connections - [Inflation, Unemployment and Growth](https://lightmysky.com/learn/civics-and-economics/inflation-unemployment-and-growth-mt_Zr0YyQwtKy) ## Opens up - [GDP: Measuring an Economy and What It Misses](https://lightmysky.com/learn/civics-and-economics/gdp-measuring-an-economy-and-what-it-misses-mt_JFm9bVs0_n) - [Counting the Past](https://lightmysky.com/learn/history/counting-the-past-mt_U3Fc_UVWJ5)