Ralph S. J. Koijen

Momentum and Mean Reversion in Strategic Asset Allocation

We study a dynamic asset allocation problem in which stock returns exhibit short-run momentum and long-run mean reversion. We develop a tractable continuous-time model that captures these two predictability features and derive the optimal investment strategy in closed form. The model predicts negative hedging demands for medium-term investors, and an allocation to stocks that is nonmonotonic in the investors horizon. Momentum substantially increases the economic value of hedging time variation in investment opportunities. These utility gains are preserved when we impose realistic borrowing and short-sales constraints and allow the investor to trade on a monthly frequency.

Health and Mortality Delta: Assessing the Welfare Cost of Household Insurance Choice

We develop a pair of risk measures, health and mortality delta, for the universe of life and health insurance products. A life-cycle model of insurance choice simplifies to replicating the optimal health and mortality delta through a portfolio of insurance products. We estimate the model to explain the observed variation in health and mortality delta implied by the ownership of life insurance, annuities including private pensions, and long-term care insurance in the Health and Retirement Study. For the median household aged 51 to 57, the lifetime welfare cost of market incompleteness and suboptimal choice is 3.2% of total wealth.

Collective pension schemes and individual choice

Collective pension schemes are the dominant form of saving for retirement in the Netherlands. We investigate the introduction of individual choices into a collective pension system without affecting the generally accepted advantages of a collective agreement. Increasing individual choices can be beneficial, as it prevents pension plans from making decisions for the average plan participant that may not be optimal for individual participants. We argue for a system in which individuals choose from a set of low-cost balanced index funds, together with a level of intergenerational guarantees that are exchange-traded. This system maintains the two primary advantages of collective agreements: risk sharing and low implementation costs, while facilitating different risk taking behavior at the individual level. To facilitate individual choices within collective pension schemes, it is important to enhance the transparency associated with intergenerational guarantees to all participants in the scheme, both in terms of their price and quantity. We argue that the current system, in which long-term guarantees are given by the young to the old within a specific fund but not across pension funds, is not transparent and we argue that it can be suboptimal. We propose a system of Pension Guarantee Exchanges (PGEs) that increase transparency and allow pension funds with different age distributions to trade with each other. Knowing the price of such guarantees facilitates the introduction of individual portfolio choices within collective pension schemes.

Likelihood-Based Estimation of Exactly-Solved Present-Value Models

We develop a tractable exactly solved present-value model to study the dynamics of stock returns, dividend growth rates, and the price-dividend ratio. We show that standard predictive regressions of returns and dividend growth rates on the lagged price-dividend ratio suffer from a problem that is akin to an errors-in-variables problem. By using non-linear filtering techniques to estimate the structural parameters of our present-value model, we can mitigate this errors-in-variables problem. We then use this framework to decompose the price-dividend ratio and excess stock returns, and study the influence of approximation errors that would arise if we were to log-linearize the model. Our model induces heteroscedasticity in returns, even though the latent processes for expected returns and expected dividend growth rates are homoscedastic.

The Fragility of Market Risk Insurance

Insurers sell retail financial products called variable annuities that package mutual funds with minimum return guarantees over long horizons. Variable annuities accounted for

Quantitative Easing in the Euro Area: The Dynamics of Risk Exposures and the Impact on Asset Prices

1.5 trillion or 34 percent of U.S. life insurer liabilities in 2015. Sales fell and fees increased after the 2008 financial crisis as the higher valuation of existing liabilities stressed risk-based capital. Insurers also made guarantees less generous or stopped offering guarantees entirely to reduce risk exposure. We develop an equilibrium model of insurance markets in which financial frictions and market power are important determinants of pricing, contract characteristics, and the degree of market incompleteness.

Risk of Life Insurers: Recent Trends and Transmission Mechanisms

We use new data on security-level portfolio holdings of institutional investors and households in the euro area to understand the impact of the ongoing asset purchase programme of the European Central Bank (ECB) on the dynamics of risk exposures and on asset prices. We develop a tractable measurement framework to quantify the dynamics of euro-area duration, sovereign and corporate credit, and equity risk exposures as the programme evolves. We propose an instrumental-variables estimator to identify the impact of central bank purchases on sovereign bonds on sovereign bond yields. Our results suggest that the foreign sector sells most in response to the programme, followed by banks and mutual funds, while the purchases of insurance companies and pension funds are positively related to purchases by the ECB.

Is the Insurance Sector at Risk

We summarize recent trends in risk exposure for U.S. life insurers from variable annuities, shadow insurance, securities lending, and derivatives. We discuss how these sources of risk could be amplified and transmitted to the rest of the financial sector and the real economy. More complete and transparent financial statements are necessary to accurately assess the overall risk mismatch in the insurance industry. We suggest ways to disclose relevant information and discuss some implications for insurance regulation.

Financing the War on Cancer

In the wake of the financial crisis, the insurance sector has been overlooked. Ralph SI Koijen and Motohiro Yogo shed new light on the rise of shadow insurance and increasing risk levels in American life insurance markets.

On the Timing and Pricing of Dividends: Web Appendix

We estimate the benefit of life-extending medical treatments to life insurance companies. Our main insight is that life insurance companies have a direct benefit from such treatments as they lower the insurer’s liabilities by pushing the death benefit further into the future and raise future premium income. We apply this insight to immunotherapy, treatments associated with durable gains in survival rates for a growing number of cancer patients. We estimate that the life insurance sector’s aggregate benefit from FDA approved immunotherapies is