The profitability of momentum investing

Friedrich, Ekkehard Arne (2010-03)

Thesis (MScEng (Industrial Engineering))--University of Stellenbosch, 2010.

Thesis

ENGLISH ABSTRACT: Several studies have shown that abnormal returns can be generated simply by buying past winning stocks and selling past losing stocks. Being able to predict future price behaviour by past price movements represents a direct challenge to the Efficient Market Hypothesis, a centrepiece of contemporary finance. Fund managers have attempted to exploit this effect, but reliable footage of the performance of such funds is very limited. Several academic studies have documented the presence of the momentum effect across different markets and between different periods. These studies employ trading rules that might be helpful to establish whether the momentum effect is present in a market or not, but have limited practical value as they ignore several practical constraints. The number of shares in the portfolios formed by academic studies is often impractical. Some studies (e.g. Conrad & Kaul, 1998) require holding a certain percentage of every share in the selection universe, resulting in an extremely large number of shares in the portfolios. Others create portfolios with as little as three shares (e.g. Rey & Schmid, 2005) resulting in portfolios that are insufficiently diversified. All academic studies implicitly require extremely high portfolio turnover rates that could cause transaction costs to dissipate momentum profits and lead the returns of such strategies to be taxed at an investor’s income tax rate rather than her capital gains tax rate. Depending on the tax jurisdiction within which the investor resides these tax ramifications could represent a tax difference of more than 10 percent, an amount that is unlikely to be recovered by any investment strategy. Critics of studies documenting positive alpha argue that momentum returns may be due to statistical biases such as data mining or due to risk factors not effectively captured by the standard CAPM. The empirical tests conducted in this study were therefore carefully designed to avoid every factor that could compromise the results and hinder a meaningful interpretation of the results. For example, small-caps were excluded to avoid the small firm effect from influencing the results and the tests were conducted on two different samples to avoid data mining from being a possible driver. Previous momentum studies generally used long/short strategies. It was found, however, that momentum strategies generally picked short positions in volatile and illiquid stocks, making it difficult to effectively estimate the transaction costs involved with holding such positions. For this reason it was chosen to test a long-only strategy. Three different strategies were tested on a sample of JSE mid-and large-caps on a replicated S&P500 index between January 2000 and September 2009. All strategies yielded positive abnormal returns and the null hypothesis that feasible momentum strategies cannot generate statistically significant abnormal returns could be rejected at the 5 percent level of significance for all three strategies on the JSE sample. However, further analysis showed that the momentum profits were far more pronounced in “up” markets than in “down” markets, leaving macroeconomic risk as a possible explanation for the vast returns generated by the strategy. There was ample evidence for the January anomaly being a possible driver behind the momentum returns derived from the S&P500 sample.

AFRIKAANSE OPSOMMING: Verskillende studies het gewys dat abnormale winste geskep kan word deur eenvoudig voormalige wenner aandele te koop en voormalige verloorder aandele te verkoop. Die moontlikheid om toekomstige prysgedrag te voorspel deur na prysbewegings uit die verlede te kyk is ‘n direkte uitdaging teen die “Efficient Market Hypothesis”, wat ’n kernstuk van hedendaagse finansies is. Fondsbestuurders het gepoog om hierdie effek te benut, maar akademiese ondersteuning vir die gedrag van sulke fondse is uiters beperk. Verskeie akademiese studies het die teenwoordigheid van die momentum effek in verskillende markte en oor verskillende periodes uitgewys. Hierdie akademiese studies benut handelsreëls wat gebruik kan word om te bepaal of die momentum effek wel in die mark teenwordig is al dan nie, maar is van beperkte waarde aangesien hulle verskeie praktiese beperkings ignoreer. Sommige studies (Conrad & Kaul, 1998) vereis dat 'n sekere persentasie van elke aandeel in die seleksie-universum gehou moet word, wat in oormatige groot aantal aandele in die portefeulle tot gevolg het. Ander skep portefeuljes met so min as drie aandele (Rey & Schmid, 2005), wat resulteer in onvoldoende gediversifiseerde portefeuljes. Die hooftekortkoming van alle akademiese studies is dat hulle portefeulleomsetverhoudings van hoër as 100% vereis wat daartoe sal lei dat winste uit sulke strategieë teen die belegger se inkomstebelastingskoers belas sal word in plaas van haar kapitaalaanwinskoers. Afhangende van die belastingsjurisdiksie waaronder die belegger val, kan hierdie belastingseffek meer as 10% beloop, wat nie maklik deur enige belegginsstrategie herwin kan word nie. Kritici van studies wat abnormale winste dokumenteer beweer dat sulke winste ‘n gevolg kan wees van statistiese bevooroordeling soos die myn van data, of as gevolg van risikofaktore wat nie effektief deur die standaard CAPM bepaal word nie. Die empiriese toetse is dus sorgvuldig ontwerp om enige faktor uit te skakel wat die resultate van hierdie studie sal kan bevraagteken en ‘n betekenisvolle interpretasie van die resultate kan verhinder. Die toetse sluit byvoorbeeld sogenaamde “small-caps” uit om die klein firma effek uit te skakel, en die toetse is verder op twee verskillende monsters uitgevoer om myn van data as ‘n moontlke dryfveer vir die resultate uit te skakel. Normaalweg toets akademiese studies lang/ kort nulkostestrategieë. Dit is gevind dat momentum strategieë oor die algemeen kort posisies kies in vlugtige en nie-likiede aandele, wat dit moeilik maak om die geassosieerde transaksiekoste effektief te bepaal. Daar is dus besluit om ’n “lang-alleenlik” strategie te toets. Drie verskillende strategieë is getoets op ‘n steekproef van JSE “mid-caps” en “large-caps” en op ‘n gerepliseerde S&P500 index tussen Januarie 2000 en September 2009. Alle strategieë het positiewe abnormale winste opgelewer, en die nul hipotese dat momentum strategieë geen statisties beduidende abnormale winste kan oplewer kon op die 5% vlak van beduidendheid vir al drie strategieë van die JSE monster verwerp word. Verdere analiese het wel getoon dat momentumwinste baie meer opvallend vertoon het in opwaartse markte as in afwaartse markte, wat tot die gevolgtrekking kan lei dat makro-ekonomiese risiko ‘n moontlike verklaring kan wees. Daar was genoegsaam bewyse vir die Januarie effek as ‘n moontlike dryfveer agter die momentum-winste in die S&P500 monster.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/4373
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