When Italian economist Vilfredo Pareto observed in 1904 that 20% of the peapods in his garden contained 80% of the total peas, he could hardly have imagined he was creating a blueprint for many 21st century business models.

Fast-forward 100 years and Pareto's Principle - which states that around 20% of something is responsible for 80% of the result - is a general rule of thumb for any salesperson worth their salt. It is particularly relevant to bulge- bracket equities divisions, which are fast realising that focusing on the few clients that really make a difference is essential to being a profitable enterprise.