Editing Openai/6936126b-3ed0-8003-aa64-374e59b4ad27 (section)

==== 1. Backtest period: 7-Dec-2020 → 7-Dec-2025 (exactly 5 years, ending today). ====
# Contribution timing: £20,000 invested once per year on each anniversary: 7-Dec of 2020, 2021, 2022, 2023 and 2024 (five contributions total).
# Top-5 definition / dates: “Top 5 biggest US stocks by market capitalisation” as of the investment date (i.e., the market-cap ranking on each 7-Dec). I will use widely-published year-end/top lists (e.g., Wikipedia / VisualCapitalist / company market-cap data) to determine that day’s top-5.
# Trading rules implemented exactly as you wrote: at each year-end (on each 7-Dec) any holding that is no longer in that day’s top-5 is sold that day; holdings that remain are kept; immediately after selling, any free cash is re-invested that same day into the then-current top-5 in equal weights (so every trade happens only on the yearly rebalancing date).
# Transaction costs / slippage: 0.1% per trade (buy or sell).
# Dividends: total-return (dividends reinvested into the same stock at the execution price on that day).
# Fractional shares allowed so we can invest exact cash amounts.
# Currency: you asked in GBP — I will convert historical USD prices to GBP using historical FX (USD/GBP) on the same trade dates. Final results reported in GBP.
# Stock tickers: I will use the primary US tickers for the top companies (e.g., AAPL, MSFT, AMZN, GOOGL/GOOG, META, NVDA, TSLA, etc. — whichever are the top-5 on each date).
# Data sources: I will pull daily historical adjusted prices and market caps from reputable public sources (Yahoo Finance / CompaniesMarketCap / Wikipedia / VisualCapitalist) and include citations.

If you’re good with those assumptions I’ll run the backtest now and return:
* A summary P&L (final NAV, CAGR, total return),
* Annualized volatility & max drawdown,
* A calendar of yearly trades (dates, tickers, shares, cash flows),
* A chart of portfolio value (GBP) over time, and
* Downloadable CSV of all trades and daily NAV.

Tell me “Go ahead” if you’re happy with the assumptions above — I’ll run it and deliver the full results.