It has been a propitious period for equity investors; over the previous five years they have enjoyed stellar returns, depressed volatility and relatively few instances of material drawdown. The prolonged nature of this environment risks the abnormal coming to be seen as normal, and our bias towards what is recent and available leading to expectations becoming untethered from reality. This could have profound implications for how we perceive (or ignore) risk and how portfolios are constructed.

The success of equities on a risk-adjusted basis in recent years can be framed in a different fashion – the failure of diversification. Against a backdrop where equities have delivered strong performance with reduced risk (compared to history) there has been scant reward for holding assets that are regarded as diversifying or that may offer insulation in a more inclement economic landscape. Indeed, diversification has come at a cost.

There is a real danger that the current environment is leading investors to worry about the wrong things. Rather than believing that prudent diversification is evermore important because of the unusually strong results delivered by equity markets; we do the opposite and start to question the role in our portfolios of those assets that have failed to keep pace with the ascent of equities. In recent years very few assets compare favourably to equities – so why hold anything else? We spend far too little time critically assessing the things in our portfolios that are out/over performing.

Arguments in support of diversification are made all the more difficult by the fact that equities have exhibited such low ‘risk’ in recent years (by way of realised volatility and drawdowns), a scenario that inescapably breeds complacency. There are technical and psychological aspects to this problem. From a technical standpoint, it is possible to build equity heavy portfolios with low ex-ante risk (in terms of volatility) if their look-back period is only three or five years. From a psychological perspective, memories of the stress and fear that can at times characterise the ownership of equities have been all but extinguished. We can easily recall equities makeing consistent upwards progression, not them halving in value.

The unusually strong risk-adjusted performance of equities has also created a process versus outcome problem, where simply being long equity risk has been consistently rewarded, irrespective of whether it was a prudent course of action ex-ante. Our pronounced tendency to judge the quality of a decision or process simply by its outcome means that we will look more favourably on less diversified, equity-centric portfolios. The corollary of this is that the pressure of unfavourable performance comparisons could lead to diversified portfolios being ‘forced’ to assume more equity risk.

The idea of diversification is to create a portfolio that is designed to meet the requirements of an investor through a range of potential outcomes – it should be as forecast-free as possible. It is also founded on the concept of owning assets that not only provide diversification in a quantitative sense (through low historic correlations) but also sound economic reasons as to why their return stream is likely to differ from other candidate asset classes. Crucially, in a genuinely diversified portfolio not all of the assets or holdings will be delivering strong results at any given time, indeed, if all of the positions in a portfolio are ‘working’ in unison – it will feel like a success but actually represent a shortcoming.

That is not to suggest that we should persist with assets or positions in a portfolio simply because they are diversifying (or have not gone up as much as equities). Rather that we should always remember the long-term benefits of diversification, and consider the merits of all holdings in a portfolio based on their own characteristics and their role amongst a mix of assets or strategies.

Our obsession with outcomes, focus on spurious reference points and our desire for action, makes remaining diversified incredibly challenging. In an equity bull market, we often struggle to see the laggard assets in our portfolio as distinctive and differentiated – serving the role they were required for – we instead identify weakness and something that needs to be addressed. This is exacerbated by the fact that in such periods the returns of everything gets compared to equities – whether the comparisons are valid or not is irrelevant.

At this point in the cycle the temptation to abandon the concept of prudent portfolio diversification is likely to prove particularly strong; but unless a new paradigm is upon us, investors will be well-served remaining faithful to sound and proven investment principles.  Take the long-term view and remain diversified.