OBR Forecast Impact Estimator

A web application that uses PolicyEngine to estimate the impact of different Office for Budget Responsibility (OBR) forecasts, including the upcoming Spring 2025 forecast (March 27, 2025).

Technology Stack

• Backend: FastAPI (Python 3.10)
• Frontend: Next.js with TypeScript
• Dependency Management: pip (Python), npm (JavaScript)
• Visualization: Recharts
• UI Framework: Radix UI
• Deployment: Docker, Google Cloud Platform
• Simulation: PolicyEngine UK

Prerequisites

• Python 3.10+
• Node.js and npm
• Docker (for containerized deployment)

Development Setup

For development, you can run the frontend and API separately using the included Makefile:

# Install dependencies
make install

# Start development services
make dev

This will start:

• Backend API server at http://localhost:8000
• Frontend development server at http://localhost:3000

You can also run services individually:

# Run only the API
make api

# Run only the frontend
make frontend

Docker Deployment

The simplest way to run the complete application is with Docker:

# Build the Docker image
make docker-build

# Run the container
make docker-run

Or use Docker commands directly:

# Build the Docker image
docker build -t obr-forecast .

# Run the container
docker run -p 8000:8000 obr-forecast

The application will be available at http://localhost:8000

Project Structure

.
├── api/                      # FastAPI backend
│   ├── endpoints/            # API route handlers
│   │   └── forecasts.py      # Forecast-related endpoints
│   ├── utils/                # Utility functions
│   │   └── forecast.py       # OBR forecast simulation logic
│   └── main.py               # API entry point
├── frontend/                 # Next.js frontend
│   ├── components/           # React components
│   │   ├── ForecastSelector.tsx    # Forecast selection component
│   │   ├── GrowthRatesInput.tsx    # Growth factor input component 
│   │   └── ForecastResults.tsx     # Results visualization component
│   ├── pages/                # Next.js pages
│   ├── public/               # Static assets
│   └── styles/               # CSS styles
├── Dockerfile                # Docker configuration
├── Makefile                  # Development commands
├── pyproject.toml            # Python project configuration
├── setup.py                  # Python package configuration
└── README.md                 # Project documentation

Features

OBR Forecast Simulation

The application uses PolicyEngine to simulate the impact of economic forecasts on UK households:

1. Growth Factors: Users can adjust several economic parameters:

   • Earned Income Growth: Wage and salary growth rate
   • Mixed Income Growth: Self-employment and business income growth
   • Capital Income Growth: Investment, dividend and interest income growth
   • Inflation Rate: General price level changes

2. Impact Metrics:

   • Median Household Income: Shows how income changes over the forecast period
   • Poverty Rate: Tracks changes in the poverty headcount ratio

3. Analysis Period:

   • Baseline year: 2025
   • Forecast period: 2026-2030

Technical Implementation

• The frontend allows users to configure growth assumptions for each year and economic factor
• The API applies these growth factors to a representative sample of UK households using PolicyEngine
• Results are calculated by comparing household outcomes across the forecast period

GCP Deployment

The application is containerized for easy deployment to Google Cloud Platform using Cloud Run or Google Kubernetes Engine.

License

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