This paper considers the recent underperformance of the equal weighted portfolio of South African Top 40 stocks relative to the market capitalisation weighted portfolio. It highlights the impact of the increased concentration of market capitalisation weights in the Top 40, which is currently at extreme levels. Furthermore, lower levels in the benefits of diversification, through higher average correlations, has reduced the positive impact of rebalancing. Finally, the turnover in index constituents has been higher than average in recent years and this has caused a further drag on performance. The combination of these effects has had a negative impact on the equal weighted portfolio’s relative performance. A rudimentary linear model, with these factors as inputs, that highlights the importance of monitoring these drivers to improve the equal weighted portfolio’s relative performance is presented.