Data Sources

Where the inflation and interest rate data used by this calculator comes from — fully documented and transparent.

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Overview

This page documents every data source used by InflationMultiplier.com. All inflation data is retrieved from the World Bank Open Data API at the time you use the calculator — no historical data is cached on our servers, and no user inputs are transmitted to us.

Transparency first: We believe users should always be able to verify where data comes from. Every data point shown on this site can be independently verified through the sources listed below.

Primary Inflation Data Source

The core inflation figure used in all calculations comes from the World Bank's World Development Indicators database.

  • Provider: World Bank Group
  • Dataset: World Development Indicators (WDI)
  • Indicator: FP.CPI.TOTL.ZG — "Inflation, consumer prices (annual %)"
  • Coverage: 189+ countries worldwide
  • Frequency: Annual
  • Typical lag: 1–2 years behind the current calendar year
  • Licence: World Bank open data licence — free to use with attribution
  • Official page: data.worldbank.org/indicator/FP.CPI.TOTL.ZG

What it measures: Annual percentage change in the cost of a representative basket of goods and services consumed by the average household. This is the standard international definition of consumer price inflation.

API endpoint used:

https://api.worldbank.org/v2/country/{code}/indicator/FP.CPI.TOTL.ZG?format=json&mrv=1&per_page=1

The parameter mrv=1 ("most recent value") retrieves only the latest available data point. per_page=1 limits the response to a single record. The response is in JSON format and includes the year the data corresponds to.

Update process: The World Bank updates this indicator as member countries report CPI data to international statistical databases. Annual figures typically become available between 6 and 18 months after the end of the calendar year they cover.

Interest Rate Reference Data (Optional)

The calculator optionally fetches benchmark interest rates for reference. These are shown to help users choose a realistic rate to model — they are not used in any calculation unless the user manually applies them.

Deposit Interest Rate

  • Indicator: FR.INR.DPST — "Deposit interest rate (%)"
  • What it measures: The rate paid by commercial banks on term deposits, as reported to the World Bank
  • Used for: Optional "Avg Rate" reference in the calculator

Lending Interest Rate

  • Indicator: FR.INR.LEND — "Lending interest rate (%)"
  • What it measures: The rate charged by commercial banks on loans to prime customers
  • Used for: Optional "Avg Rate" reference in the calculator

Limitations of World Bank Data

  • Annual data only: The World Bank publishes annual CPI figures through this indicator. Monthly granularity is not available. For recent monthly data, refer to the national sources listed below.
  • Reporting lag: Data from a given year may not appear until 1–2 years later, depending on when each country submits its figures to the World Bank. The calculator displays the year the data corresponds to so users are aware of this.
  • CPI basket varies by country: Each country defines its own CPI basket with different weights for housing, food, transport, healthcare, and other categories. Direct comparisons between countries should be made cautiously.
  • Coverage gaps: Not all countries have data for every year. Some countries may have older or missing entries due to reporting constraints or statistical capacity issues.
  • Euro Area: For EUR, the calculator uses the Euro Area (XC or EMU) aggregate code, which represents the average across the Eurozone. Individual eurozone countries may have meaningfully different inflation rates.

Chart.js Library

  • Provider: Chart.js (open source, MIT licence)
  • Delivery: Loaded from cdn.jsdelivr.net
  • Purpose: Renders the growth-over-time line chart in the calculator
  • Data involved: No external data — the chart displays only the calculator's own output values. No data is sent to Chart.js or jsDelivr.

IP Geolocation (Optional, First Visit Only)

On a first visit, the calculator optionally queries public IP geolocation APIs to auto-detect your country and set the default currency to the one most relevant to you. This is a convenience feature only — if auto-detection fails or is blocked, the calculator defaults to USD.

Services queried in order:

  1. ipapi.co — returns country code and currency code. Queried first because it provides the currency directly.
  2. api.country.is — returns country code only (used as a fallback; currency is then inferred from country).
  3. Browser timezone — used as a final fallback with no network request if both API calls fail or return an error.

We do not store or log IP addresses or geolocation data. The request is made by your browser directly to these third-party services. Their privacy policies apply to that request.

What We Do Not Store

  • No inflation data is cached or stored on our servers — every request goes directly to the World Bank API from your browser.
  • No user inputs (principal, rate, years, currency) are sent to our servers.
  • No calculation results are logged by us.
  • No cookies are set by our server. Local browser storage (localStorage) is used only to save your preferred color theme.

National Data Sources (Reference)

For the most recent monthly inflation data — particularly if the World Bank data lags — consult national statistics offices directly:

These sources publish monthly CPI data, typically within 2–4 weeks of the end of the reference month, making them more current than the annual World Bank figures.