Methodology

What the numbers are

Each portfolio is run on a simulated paper account through the same decision process throughout: candidates are ranked, a decision is recorded, the positions are implemented on the paper account, and the account is reconciled against the broker's own statement. The published line is an index set to 100 on the first day of the record. Each day's move is the account's return for that day, with deposits and withdrawals removed so that only investment results move the line.

What the record starts from

The record begins on the inception date shown on each portfolio. There is no backtest before it, and none is joined onto it. Any historical simulation, if shown, is labelled as such and kept on a separate chart.

What is not shown

Account sizes and balances are not published; the index is what matters and a paper balance invites comparison with real money. Paper fills do not bear real market impact, so the costs of doing the same thing with real money would be higher.

The comparison line

Where a portfolio names a benchmark, its index is also set to 100 on the portfolio's first day and moved by the benchmark's own close-to-close change on each of the portfolio's published days (the last close on or before that day; adjusted for dividends where the data source provides it). A benchmark close more than a week old is treated as missing and the line stops there rather than being filled in.

How the figures are calculated

Every figure is calculated from the published daily index, each time the page loads; none is typed in. Volatility is the standard deviation of daily returns scaled by the square root of 252. Beta is the covariance of the portfolio's daily returns with the benchmark's, divided by the benchmark's variance, over the same days. Results on a sale are measured against the average cost of the shares held; where that cost cannot be established from the record the result is shown as unknown rather than estimated. Trade sizes are shown as a share of the portfolio on the previous day, not in currency.

How the record is protected

Every published day is written once, by the system, after the day's accounts are rebuilt. It cannot be edited afterwards: if the underlying accounts are ever corrected for a day that has already been published, publishing stops and the correction is disclosed rather than silently applied. See Verification.