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Overview

The PPP package uses official economic data from the World Bank to calculate fair, purchasing-power-adjusted prices across different countries. This ensures your pricing reflects real-world economic conditions rather than arbitrary conversions.

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World Bank Indicator

The package uses the Price Level Ratio of PPP conversion factor (GDP) to market exchange rate indicator.
Indicator Code: PA.NUS.PPPC.RFThis indicator measures the ratio of purchasing power parity (PPP) conversion factor to market exchange rate. It shows how much a basket of goods that costs $1 in the United States would cost in another country.

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What This Means

The Price Level Ratio tells you the relative cost of living in each country compared to the United States:
  • ~0.29 (Sri Lanka) → Goods cost approximately 29% of US prices
  • 1.0 (United States) → Baseline reference point
  • >1.0 (Switzerland ~1.08) → Goods are more expensive than in the US

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Data Collection Process

The package maintains up-to-date PPP data through an automated update script located at scripts/update-data.js.

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How Data is Sourced

  1. Downloads Excel file from the World Bank API: 
    https://api.worldbank.org/v2/country/all/indicator/PA.NUS.PPPC.RF?downloadformat=excel
  2. Processes the Excel data using the XLSX library to extract country-specific ratios
  3. Selects the most recent data for each country by iterating through years in reverse order
  4. Stores dual country codes in data.json:
    • 3-letter ISO codes (e.g., LKA)
    • 2-letter ISO codes (e.g., LK)

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Data Structure

The processed data is stored in data.json as a simple key-value map: 
{
  "LKA": 0.28885598326474304,
  "LK": 0.28885598326474304,
  "USA": 1,
  "US": 1,
  "CHE": 1.077727161298933,
  "CH": 1.077727161298933
}
Both 2-letter and 3-letter codes point to the same value, allowing flexible lookups regardless of which format you use.

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Update Frequency

The World Bank typically updates PPP indicators annually. The data reflects economic conditions from the previous year.

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When to Update

You should update the package data:
  • Annually - When the World Bank releases new PPP data (usually mid-year)
  • After major economic events - Currency crises, significant inflation, or policy changes
  • Before major pricing decisions - Ensure you’re working with current data

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Running the Update Script

To update the data yourself: 
cd scripts
node update-data.js
The script will:
  1. Download the latest Excel file from the World Bank
  2. Parse and process the data
  3. Update data.json with the most recent values
  4. Display a summary of countries processed

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Data Coverage

The package currently includes PPP ratios for 200+ countries and territories, covering:
  • All major economies
  • Most developing nations
  • Many territories and island nations
  • Special administrative regions (Hong Kong, Macau)

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Missing Countries

If a country code is not found in the data, the ppp() function returns null. This can happen for:
  • Very small territories without economic data
  • Regions in conflict where data collection is impossible
  • Newly formed nations not yet in the World Bank database

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Data Quality

The World Bank collects this data through:
  • International Comparison Program (ICP) - Coordinated global price surveys
  • National statistical offices - Official government data
  • Regional coordinators - Ensure consistency across countries
The PPP conversion factors are calculated using detailed price data for hundreds of goods and services, weighted by consumption patterns in each country.

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Learn More

For detailed information about the World Bank’s methodology:

World Bank Indicator Documentation

View official documentation, methodology, and historical data for the PA.NUS.PPPC.RF indicator

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