25-07-2014 | インサイト

Choices relating to asset allocation have major effect on the risk/return characteristics of investment portfolios. New academic insights have led to important innovations in this area. One of these is implementing a market view in a risk-parity portfolio.

- Mean variance solutions too sensitive to expected returns
- Risk parity does not use market views, however strong
- Researchers create bridge between the two methods
- Degree of confidence in views affects asset allocation

In our present challenging investment environment, it is important for pension funds and other institutions to make use of the opportunities offered by innovations in asset allocation. In a knowledge-sharing session held in May, Robeco discussed three such new developments: 'mean variance versus risk parity', 'global diversified carry' and 'strategic allocation to commodity factor premiums'. These are innovations that - as the session showed - can all come up trumps by adding value to a portfolio. In this first of three articles we look at the implementation of a market view in a risk parity portfolio.

最新の「インサイト」を読む

配信登録
For a long time, portfolio managers based their asset allocation on 'mean variance' - the method linked to the modern portfolio theory of weighing (expected) risk against return. Roderick Molenaar, portfolio strategist at Robeco, describes this method of portfolio optimization as 'a mathematically satisfactory solution', though one that has fallen in popularity, and not without good reason.

Starting in the late 1990s, investment professionals increasingly began to favor risk-based solutions in determining their strategic asset allocation. Mean variance solutions had become too sensitive to expected returns: small adjustments led to major portfolio changes. Risk parity solutions (in which expected returns do not play a role) gained in popularity. Triggered by the financial crisis of 2007-2009, this movement took on landslide proportions. Determining the right parameters for portfolio construction turned out to be more difficult than imagined in previous decades.

"Skepticism about relying fully on a market view increased,” says Molenaar. “Expectations were often uncertain, but they still had a huge impact. You have to be very sure of your view to be able to rely on it completely. Mean variance could also produce a concentrated risk profile in a portfolio. Investment professionals wanted to get away from this."

‘You have to be very sure of your view to be able to rely on it completely.’

This resulted in strategies that partly disregarded expected returns. Risk parity, or as Molenaar prefers, 'equal risk contribution', became popular as a method of setting up portfolios in such a way that the different investment categories held in a portfolio made up an equal risk budget. In practical terms, this often means that exposure to bonds will be much greater relative to equities when compared to a portfolio constructed on the basis of mean variance.

"Choosing a specific strategy is linked to the degree of confidence you have in your data on expected returns, volatility and correlations," says Molenaar. The strategist cites examples of other methods of constructing portfolios, such as maximum diversification, minimum variance, volatility parity (1/σ), risk parity and equal weighting (1/N). The methods differ from each other as regards the extent to which they include data on volatility, correlations and investment expectations in the considerations. In the case of risk parity, for instance, investors will assume that while the available information on volatility and correlations is sufficiently reliable, they cannot forecast expected returns, or can only do so inadequately.

What if an investment professional has a strong view regarding market changes? Risk diversification, a key factor in risk parity, is important, but how can you put your view to use? Risk parity is popular and has been successful for a long time,” says Molenaar. “However, in May 2013 [when the Fed first started talking about 'tapering', i.e. reducing its bond-buying program], the rise in interest rates had a heavy impact on this strategy."

He expressed a further concern: "The success of risk parity is measured mainly in terms of returns. This seems strange in itself, as portfolio construction under this strategy in fact takes place without considering returns. While with risk parity volatility is low, returns lag. And the Sharpe ratio is high, but you cannot live on that." According to Molenaar, one way of boosting returns here is to use leverage. "But is that what we want? And will the regulator agree to this?” he asks.

Molenaar thinks that since it seems that interest rates can hardly go any lower, the success of the risk parity method could be in doubt. According to various sources, the chances of rising bond yields in the coming years are considerable. "When confidence in a specific market view is strong, you would do well as an investment professional to implement it,” he says. “But the big question is how to proceed if you have constructed your portfolio on the basis of risk parity. In the strength of risk parity also lies its weakness: it does not use market views, however strong."

‘In the strength of risk parity also lies its weakness’

According to Molenaar, the Black & Litterman model (which provided a solution in the 1990s to the problems surrounding the assessment of expected returns on investment categories), can also introduce market views into risk parity portfolios. Based on Bayesian techniques, Molenaar and his fellow researchers show how optimized portfolios can be influenced, depending on the amount of confidence there is in such views. The amount of confidence in a view is central to the solution studied. If there is very little or none, the portfolio manager will construct the portfolio around risk parity. If there is substantial confidence, asset allocation will resemble that for a traditional mean variance portfolio. As a function of the degree of confidence, the weights of the investment categories will be determined by a mix of both extremes.

"Our starting point is a portfolio based on risk parity, and depending on the way confidence in a market view increases, the portfolio will start to resemble the mean-variance portfolio that goes with that projection,” says Molenaar. “This way we can create a bridge between the two strategies. The best of both worlds come together.”

A practical problem that Molenaar highlights is the challenge posed by the quantification of the degree of confidence in a view. Hans de Ruiter, CIO at the TNO pension fund, picks up on this point in his response to Molenaar's research. He points out, for instance, that the findings from the behavioral finance literature show that investment professionals are generally not particularly good at estimating risk parameters. De Ruiter believes that Robeco's research could be supplemented by taking into account in the analysis the relative attractiveness of the different investment categories (e.g. equities performing better than bonds).

Molenaar responds in a takeaway for pension fund investment professionals that if funds work with risk parity, they would do well to look beyond just risk considerations: "If you have confidence in a view, then put it to use."

当資料は情報提供を目的として、Robeco Institutional Asset Management B.V.が作成した英文資料、もしくはその英文資料をロベコ・ジャパン株式会社が翻訳したものです。資料中の個別の金融商品の売買の勧誘や推奨等を目的とするものではありません。記載された情報は十分信頼できるものであると考えておりますが、その正確性、完全性を保証するものではありません。意見や見通しはあくまで作成日における弊社の判断に基づくものであり、今後予告なしに変更されることがあります。運用状況、市場動向、意見等は、過去の一時点あるいは過去の一定期間についてのものであり、過去の実績は将来の運用成果を保証または示唆するものではありません。また、記載された投資方針・戦略等は全ての投資家の皆様に適合するとは限りません。当資料は法律、税務、会計面での助言の提供を意図するものではありません。

ご契約に際しては、必要に応じ専門家にご相談の上、最終的なご判断はお客様ご自身でなさるようお願い致します。

運用を行う資産の評価額は、組入有価証券等の価格、金融市場の相場や金利等の変動、及び組入有価証券の発行体の財務状況による信用力等の影響を受けて変動します。また、外貨建資産に投資する場合は為替変動の影響も受けます。運用によって生じた損益は、全て投資家の皆様に帰属します。したがって投資元本や一定の運用成果が保証されているものではなく、投資元本を上回る損失を被ることがあります。弊社が行う金融商品取引業に係る手数料または報酬は、締結される契約の種類や契約資産額により異なるため、当資料において記載せず別途ご提示させて頂く場合があります。具体的な手数料または報酬の金額・計算方法につきましては弊社担当者へお問合せください。

当資料及び記載されている情報、商品に関する権利は弊社に帰属します。したがって、弊社の書面による同意なくしてその全部もしくは一部を複製またはその他の方法で配布することはご遠慮ください。

商号等： ロベコ・ジャパン株式会社 金融商品取引業者 関東財務局長（金商）第２７８０号

加入協会： 一般社団法人 日本投資顧問業協会

本記事に関連するテーマ：