Читать книгу The Foreign Exchange Matrix - Barbara Rockefeller - Страница 14

The FX Matrix refers to a grid format of the multiple factors and players in the FX market and the way they interact. The term matrix is borrowed from random matrix theory and we use the matrix concept as a metaphor to help you avoid reaching or accepting oversimplified explanations of why the market behaves the way it does.

In random matrix theory, the maths is truly advanced. Graduate students, hedge funds and governments devise models of complex dynamic systems. Most of us can’t get past page one of their articles and books because of the daunting calculations, but the metaphor is helpful to get a general grasp of the idea. In finance, random matrix theory was borrowed from physics and used to do things like remove idiosyncratic noise from correlation studies in designing optimum portfolios, leading to better estimates of component risk. The factor modelling includes weighting endogenous variables, exogenous variables and unobserved factors, and measuring their vectors.

Most relevant to the FX market today is estimating effects like sovereign risk contagion. Central bankers, including the Federal Reserve, are avid practitioners. ^[1] As the European Monetary Union (EMU) grapples with bank capital adequacy and sovereign credit issues, it’s a pretty good assumption that European economists are using matrix theory, too.

The 2008 failure of Lehman Brothers (considered a local behaviour) jumped the boundaries of its own (large) matrix and became a universal factor independent of the pre-existing probability distributions of the other matrices. In the vernacular, a falling tide lowers all boats. But we want to know whether the factors involved in the Lehman failure (including the behaviour of the US government) were random noise to the FX market, or an exogenous factor (out of left field), or maybe an endogenous (inherent) factor in the FX matrix. Some correlations are, after all, just coincidence. Millions of random correlations exist in the financial world. We want to know how much weight to give Big Financial Institution Failure and Government Refusal to Intervene in the FX matrix.

Lehman Brothers declared bankruptcy on 15 September 2008. Before then, the rumour mill was already active with word of the bankruptcy. We heard of European banks closing lines to Lehman several months before the final collapse. Lehman wasn’t the only factor in the FX market, but consider the trajectory of the dollar index. It had bottomed in March 2008 (at 70.698) and put in a second low in July (71.314) but then rose to 80.375 by 11 September. Over the next week, encompassing the Lehman debacle, the dollar index fell to what turned out to be an intermediate low of 75.891 on 22 September. The index then rose to a high of 88.463 by late November. The dollar’s rise was a surprise to those FX players accustomed to selling the currency of a country in trouble. The dollar’s use as a safe-haven trumped the negativity of Lehman’s bankruptcy and therefore gave the safe-haven status more weight in the matrix.

The dollar index was already on the upswing when Lehman went bankrupt and the sell-off on the actual bankruptcy news was very short-lived; only one week. Smart FX analysts were detecting that overall financial market risk aversion was in play over the summer of 2008 and the dollar kept rising. The Lehman bankruptcy in hindsight was an exogenous shock, mostly because it was inconsistent with our assumptions about how the US government behaves and how the financial sector had behaved in the past. Up until the very last minute, some observers expected a bailout like the one of Long-Term Capital in 1998, and a return to risk positioning. But once the news was digested, the FX market returned to its previous mode of shunning risk. At that time (and up to the S&P downgrade of the US sovereign rating in August 2011), to be risk averse was to buy the safe-haven dollar.