Northwest decided to try a “hub and spoke” strategy that had worked well in the North American market—wherein airplanes fly to a central location and then fan out to distant points. After comparing profiles of several European airlines, Northwest selected KLM of the Netherlands as a good candidate for its needs. It also saw how it could help KLM expand in two markets: North America and Asia. KLM had an extensive route structure in Europe and a large, modern facility at Schipol Airport in Amsterdam, which is centrally located. On paper at least, the partnership between these two carriers appeared ideal.
Some partnerships are obvious right from the start. Suppose a company wants to partner with its employees’ union to start a quality improvement process. Or perhaps a company wants to have two or more departments such as Manufacturing,Marketing, or Engineering partner on a product development project. Or a natural alliance between a customer and supplier results from the relationship already in place. Outsourcing relationships are becoming more and more common as businesses refocus on their core business and satisfying their customers’ needs.


The city is in the midst of a building boom.All over downtown, the landscape is changing as office space gets tighter and towers sprout up on once-empty street-level parking lots. One of the city’s largest,most prestigious contractors has just completed negotiations with a legal firm to build a new office tower. The location was selected, and preliminary architectural design work was completed.With the tight budget and time constraints, how could Robert, the contractor, get the job completed on time and on budget? The legal firm was currently leasing fifteen stories, and their lease was up at the end of the following year. They needed to have their new building finished by then.
What conclusions can be drawn from these observations? Portfolios that are optimized with regard to risk seem to do better than those that additionally rely on return forecasts. Sample means are not a good predictor for future returns of bond portfolios. In this context Jorion (1986) argues, that the sample mean is exposed to considerable estimation risk whereas variances and correlations are generally more stable over time. The high influence of the return vector on the weights of the tangency and equal risk portfolios can lead to extreme and volatile portfolio returns. Kallberg and Ziemba (1984) point out that errors in estimating future returns have a ten times higher impact on the out-of-sample performance of the optimized portfolio than errors in estimating the variance–covariance matrix. Similar conclusions apply when using adjusted value at risk or lower partial moments as a risk measure.
To simulate a realistic decision-making process we apply a backtesting methodology. Sample means and risk measures are estimated for the subperiod January 1987 to September 1998. In those cases where the return series is adjusted for autocorrelation the estimation of the desmoothing parameters is also based on the shortened sample period. Then the portfolios are optimized. With the obtained weights the series of monthly out-ofsample returns for each portfolio is calculated for the period October 1998 to September 2003. Based on this out-of-sample period the risk-return characteristics of the optimized portfolios and the benefits of the optimization approaches are examined.