Share:
How It Works
The CPI-based inflation rate measures how much prices have risen over a year by comparing this year's Consumer Price Index to last year's. The Fisher equation then separates nominal interest rates into real returns and inflation.
Together, these tools help investors understand whether their returns are beating inflation. A savings account paying 4% with 3% inflation yields only about 1% in real purchasing power.
Example Problem
The CPI was 295.6 last year and 304.7 this year. What is the inflation rate?
- i = (304.7 − 295.6) / 295.6 × 100
- i = 9.1 / 295.6 × 100 = 3.08%
If a bond pays 5% nominal, the Fisher equation gives a real rate of 5% − 3.08% = 1.92%.
Frequently Asked Questions
What is the Consumer Price Index?
The CPI tracks the average cost of a basket of consumer goods and services over time. The Bureau of Labor Statistics publishes it monthly. A CPI of 300 means prices are 3 times what they were in the base year (100).
What is the Fisher equation used for?
It separates a nominal interest rate into real return and inflation. If a bank offers 6% and inflation is 2.5%, the real return is about 3.5%. This helps investors compare opportunities across different inflation environments.
What causes inflation?
Inflation can be driven by excess demand (demand-pull), rising production costs (cost-push), or expansion of the money supply. Central banks target about 2% inflation as a sign of healthy economic growth.
Related Calculators
- Interest Rate Calculator — compute simple and compound interest.
- GDP Calculator — understand the broader economy.
- Rule of 72 Calculator — estimate doubling time for investments.
- Compounding & Discount Factors Calculator — time-value-of-money factors affected by inflation.
- Present Worth Analysis Calculator — evaluate future cash flows in today's dollars.
Reference: Bureau of Labor Statistics. Consumer Price Index. U.S. Department of Labor.