S&P 500 Portfolio Allocator

A command-line tool written in Rust that helps allocate investments across S&P 500 companies based on market capitalization weighting. It calculates how many shares to buy of each stock to mirror the index composition, taking into account your existing holdings.

Features

• Fetches current S&P 500 constituents via API Ninjas
• Retrieves real-time stock prices and market caps from Yahoo Finance
• Supports multiple currencies (automatically converts to USD)
• Accounts for existing portfolio holdings
• Outputs allocation recommendations to CSV

Prerequisites

• Rust (tested on 1.70+)
• An API key from API Ninjas (free tier available)

Usage

1. Clone the repository:

   git clone https://github.com/mountEvarus/sp-500-allocator.git
   cd sp-500-allocator

2. Create a .env file in the project root with your API Ninjas key:

   NINJA_API_KEY=your_api_key_here

3. Create an input/values.json file with your portfolio details:

   {
     "amount": 50000.00,
     "currency": "USD",
     "portfolio": [
       { "ticker": "AAPL", "share_count": 10 },
       { "ticker": "MSFT", "share_count": 5 }
     ]
   }

   • amount: Cash to allocate (in the specified currency)
   • currency: Your currency code (e.g., "USD", "GBP", "EUR")
   • portfolio: Your existing holdings (use an empty array [] if starting fresh)

4. Run the application:

   cargo run

5. Find your allocation recommendations in output/allocation-{timestamp}.csv

License

MIT