Performance is the single most important factor when choosing a PEP or ISA. Graphs and data given in the reviews illustrate four aspects of performance and, as the measurements used to assess them can be difficult to interpret, we have also ranked Return, Consistency and Volatility numerically. All calculations are on an 'offer to offer' basis and assume gross income is re-invested.

There are a number of different PEP and ISA investment sectors (for example UK Growth, International and UK Balanced). We review the performance of each sector as a whole and advise on its suitability for different types of investor. Since all the funds in a particular sector have the same investment opportunities, we examine whether a fund has successfully added value over and above the growth of its peer group.