Abstract: While it is evident that market concentration on the JSE is largely responsible for much of the inefficiencies of existing equity benchmarks, liquidity also plays an increasingly important role in the determination of fund holdings as the fund’s size increases. Funds wishing to reduce concentration in their benchmark portfolios by spreading their holdings more equitably will find themselves hampered in their efforts by the need to keep holdings at levels which enable smooth entry into and exit from less liquid shares. This imposes a cap on the weights that can be attributed to shares at the tail end of the index and forces an increase in holdings in the more liquid shares at the top of the index. Given that most of these liquid, large cap shares on the exchange are resources shares, it is unsurprising that a marked shift from Financial-Industrials to Resources shares is found for optimal benchmarks as fund size increases. It is also found that, as fund size increases, the degree of deviation fund managers can take from these optimal benchmarks decreases significantly. It is noted that the constraints imposed on benchmarks by the new unit trust regulations have little impact on the results and were not violated at any stage of the optimisation. In contrast, pension fund regulations were violated prior to the maximum viable fund size indicating the limitations the proposed regulations impose on the holdings of large pension fund managers. Given the deficiencies observed in existing equity benchmarks, the methodology adopted in this paper attempts to optimise the interplay between (i) concentration, (ii) liquidity, (iii) fund size and (iv) regulatory constraints in their construction. While the specific analysis was conducted in the context of the practical issues that came to the fore with the 24 June 2002 introduction of the new FTSE/JSE Africa index series, the methodology introduced in this paper is capable of contributing to the explicit construction of more efficient benchmarks in the future.