This dissertation studies the sources of the momentum abnormal returns. The first essay attempts to find the relative role of cross-sectional and time-series variances in generating returns from the momentum strategy. By decomposing the returns from the momentum strategy both theoretically and empirically, the first essay finds that own-stock autocovariance is an important source in generating momentum returns. More interestingly, the own-stock autocovariance comes primarily from the loser portfolio. This finding provides another explanation to the recent finding that the loser portfolio is the driving force of the momentum abnormal returns. Based on the above discovery from the first essay, the second essay attempts to find out the underlying reason for the important asymmetric own-stock autocovaraince from the loser portfolio. We find that this return predictability comes from the short-selling constraints and risks. Stocks with more severe short-selling constraints prevent pessimistic information from being released into the stock prices more quickly; and thus causes those stocks to be overpriced and auto-correlated in their returns.

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This year (2018), it is 25 years since the Momentum Strategy was first scientifically described. Despite this, the cause of the effect has not surely been concluded although it has been empirically studied in several previous studies. It has been shown to be valid for different kinds of assets. Since the authors of this thesis are based in Stockholm they thought it would be interesting and relevant to study if the strategy is valid on the Swedish market. The stock data comes from the stocks which has been part of the OMXS30 at least once during the period of 2010-2018. This study has also utilised two different ways on how to quantitate the return of the different portfolios. The effect of the holding period has in this report been attempted to address. The holding period is the length of the period which assets should be enclosed in the portfolio. One of the quantitation methods compared the portfolios’ development each month. The other method was more like a window analysis, to evaluate a portfolio’s return if one decides to invest in that theory until all the invested funds has been turned over. The study finds that the Momentum Strategy with holding periods of 2, 3 and 4 months significantly outperforms the market. With a higher significance level (10%) Momentum Strategy portfolios with holding periods of 2-6 and 11-14 months are outperforming the market. With a larger sample size, it is possible that the results would have been more conclusive.

This thesis studies the sources of the returns from the momentum strategy and attempts to find some hints for the heated debate on the market efficiency hypothesis over the past twenty years. By decomposing the momentum returns from a mathematical model, we investigate directly the contributors and their relative importance in generating these momentum returns. Our empirical results support that autocorrelation of own stock returns is one of the driving forces for the momentum expected returns. The magnitude of the autocorrelation decreases as the ranking period becomes more remote. The second important source comes from the cross-sectional variation of the expected returns in the winner and loser portfolios at a given time. The third important source is the difference of the expected returns between the winner and loser portfolios. To our surprise, the cross-autocovariance does not contribute much to the momentum expected returns. Thus, the lead-lag effect can cause momentum returns, but its impact is not as significant as we had anticipated. More importantly, by changing the weights of the winner and loser portfolios, we find that the own-autocovariance of the winner portfolio is almost negligible, compared to that of the loser portfolio. The returns of the winners are much more random than those of the losers. This asymmetric own-autocovariance found in the return decomposition provides another underlying explanation to the recent finding that the contribution of the winner and loser portfolios to the momentum returns is asymmetric, and it is the losers, rather than the winners, that drive the momentum returns. Therefore, the market may not be as efficient as we believed before.

The profitability and the sources of the returns on momentum strategy have always been a popular subject of study in the financial field. Nevertheless, there exist significant discrepancies between the conclusions of the papers due to the difference in time period and the emphasis on average results. Thus, the purpose of this paper is to investigate momentum strategy with information uncertainty in Taiwan stock market during the period 1990-2009 given the basis on the research method of Jegardeesh and Titman(1993). The result shows that momentum strategy cannot averagely obtain significantly positive returns in the long run in Taiwan stock market and moreover it presents an enormous short-term reversal. Besides, in terms of business cycle, there is still no significant return on momentum strategy either; there will be significantly negative return when implementing momentum strategy in the recession of business cycle. On the other hand, from the view of investor psychological biases, it should be seen greater psychological biases owing to greater information uncertainty. As a result, a stronger stock price continuation may be observed under high information uncertainty stocks. However, the effect of information uncertainty is only pronounced among loser portfolios. To summarize, compared with the profitability and the stability of contrarian strategy, the findings support that there is no significant momentum phenomena in Taiwan stock market at all.

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Comparing the performance of a pure momentum strategy with a strategy based on intermediate past returns on OMXS 1999-2018, this study shows that a pure momentum strategy significantly outperforms a strategy based on intermediate past returns. The pure momentum strategy delivers significant returns, primarily for portfolios based on shorter formation and holding periods. Furthermore, this study show that these significant returns are not due to loading on common systematic risk factors. Moreover, this study shows that by implementing a scaling component to the pure momentum strategy, investors can mitigate the crash risk in momentum strategies to some extent.

<p>Abstract</p><p>Market efficiency is a highly debated topic within the academic research field of finance.</p><p>Several studies have presented that the return on stocks may be predictable by employing the</p><p>momentum investment strategy, which contradicts the Efficient Market Hypothesis in</p><p>exchange market. There is extensive international evidence, on an academic level that the</p><p>momentum investment strategy yields positive abnormal returns when short-term periods are</p><p>considered. This paper examines the profitability of the momentum investment strategy in</p><p>Canadian and Swedish stock markets during January 2000 to December 2006. To investigate</p><p>the strategy, two separate portfolios of winners and losers, each portfolio containing 50</p><p>stocks, are created for each market. Then the momentum strategy, which consists in long</p><p>position in past best performing stocks and short positions in past worst performing stocks, is</p><p>run for each exchange market. Results show that the strategy generates statistical significance</p><p>at the 5% level for Canadian market for 9-month holding period, and with the level of</p><p>significance at the 10% for Swedish market for the 6 and 9-month holding periods after</p><p>excluding the data for the year 2002. Moreover, results show that the strategy is even stronger</p><p>in the level of significance during the bull trend of the markets. The paper confirms the</p><p>existence of the momentum anomaly in TSX and SSE.</p>

Abstract Market efficiency is a highly debated topic within the academic research field of finance. Several studies have presented that the return on stocks may be predictable by employing the momentum investment strategy, which contradicts the Efficient Market Hypothesis in exchange market. There is extensive international evidence, on an academic level that the momentum investment strategy yields positive abnormal returns when short-term periods are considered. This paper examines the profitability of the momentum investment strategy in Canadian and Swedish stock markets during January 2000 to December 2006. To investigate the strategy, two separate portfolios of winners and losers, each portfolio containing 50 stocks, are created for each market. Then the momentum strategy, which consists in long position in past best performing stocks and short positions in past worst performing stocks, is run for each exchange market. Results show that the strategy generates statistical significance at the 5% level for Canadian market for 9-month holding period, and with the level of significance at the 10% for Swedish market for the 6 and 9-month holding periods after excluding the data for the year 2002. Moreover, results show that the strategy is even stronger in the level of significance during the bull trend of the markets. The paper confirms the existence of the momentum anomaly in TSX and SSE.

This paper examines the efficiency of the Swedish stock market, specifically the Large cap list of the Stockholm stock exchange. This is achieved by implementing the relative strength method of investing during the decade of 2010-2020 and evaluate the results in contrast to the Efficient Market Hypothesis. The relative strength method applied in this paper is the similar strategy that Jagadeesh &amp; Titman (1993) utilized. In short, the strategy is based on buying the historically best performing stocks whilst selling short the previous worst performers. Additionally, the risks associated with the method were examined with the risk measurements of the Jensen Alpha and the Modigliani risk-adjusted performance. The results indicate that the relative strength method is unable to consistently generate above-market returns, so that the study is unable to reject the Efficient Market Hypothesis. In addition, the relative strength method is unable to justify the risks associated.