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

=== Important notes / caveats about the script ===
* Market-cap snapshot method: the script computes a company’s market cap on a date as close price on that date × sharesOutstanding (from yfinance.info). sharesOutstanding is often current and may not reflect historical share counts exactly. For most large caps the difference is usually small, but it is a possible source of small inaccuracies vs. an official historical market-cap snapshot provider. If you prefer absolute accuracy, we can substitute a service that stores historical market-cap snapshots (CompaniesMarketCap or paid data vendors) — the script can be adapted to read those snapshots if you provide them or we can fetch them if allowed.
* Dividends: the script reinvests dividends on the dividend payment date into the same stock and by default does not charge transaction costs on dividend reinvestment (common simplifying assumption). If you want to charge the 0.1% tx cost on reinvested dividends, I can change that.
* FX: the script uses Yahoo Finance 'GBPUSD=X' series (which returns GBP per USD close). We convert USD amounts to GBP by multiplying USD × fx (GBP per USD). Double-check this mapping after running — if you want USD as base currency instead, change BASE_CURRENCY.
* Trade execution price: trades execute at the market close price on the trade date (common backtest assumption).
* Data quality: yfinance is free and convenient but occasionally misses data for a few tickers/dates. The script attempts to skip tickers missing data. For a production-grade backtest we’d want a premium historical prices & market-cap feed.