نشریه تحقیقات مالی
پیاپی 62 (تابستان 1400)

In network theory, centrality is a measure to estimate importance and influence of a special node to the whole network structure. The aim of this research is to investigate the characteristics of stock centrality and its reliability in risk estimation and portfolio selection.

First in this paper, we analyzed the relationship between stock’s centrality & benchmark risk estimation measures like beta & standard deviation. Then, we analyzed the relationship between stock’s centrality & Markowitz framework’s weights; and finally, we introduced centrality-based portfolio selection strategy and compared it with other benchmarks, by different portfolio performance measures.

Our observations indicate that in Tehran stock exchange, centrality can have an effective role in stocks risk estimation and there is a meaningful relation between centrality and other measures. We also observed that out that low central stocks can raise the benefits of portfolio diversification, and centrality-based portfolio selection method can have a better performance than other benchmark portfolio selection methods and results in a better risk adjusted return.

Stock centrality, as a measure to estimate importance and influence of member of a network, is capable of describing stock risk characteristics like other accepted measures. We can take advantage of this capability for portfolio selection.

The stochastic dominance theory has extensively employed in various financial fields because it is not necessary to assume a specific distribution of returns, such as normal distribution. In this research, one of its new applications has been used to identify arbitrage opportunities and consequently, to evaluate the efficiency of the market and also to analyse the investor preferences.

To this end, a new approach of estimating stochastic dominance, the quantile regression method is utilized to perform the stochastic dominance test on the daily returns of the Tehran Stock Exchange total index close values over a period of 19 years (from September 1999 to February 2019) that contains different bullish and bearish market conditions.

Data analysis suggests that no evidence has been found to reject the dominance of cumulative distribution of returns between the two periods. Thus, the non-rejection of the statistical hypothesis of the first-order stochastic dominance indicates the possibility of obtaining arbitrage profit and on the other hand, the second-order stochastic dominance test rejects the market efficiency hypothesis. The existence of a third-order stochastic dominance can also be seen as a sign of the herd behavior of investors during the upward market conditions.

The results indicate the existence of arbitrage opportunities in the Tehran Stock Exchange between bullish and bearish market conditions. Other results of this study, do not confirm the Tehran Stock Exchange efficiency hypothesis, which is consistent with most previous research about the market efficiency of the Tehran Stock Exchange. These findings also imply that risk-averse investors tend to invest in market growth cycles and suggest the existence of herd behavior during these periods.

According to the efficient market hypothesis, market efficiency refers to the condition in which prices in the markets are adjusted immediately to the new information. The speed and quality of response to new information determine the level of market efficiency. The lower speed and quality will result in lower efficiency. The weak level of market efficiency is a condition in which the price of an asset is predictable with publicly available information. In another word, prices are following a predictable pattern and not moving based on the random walk hypothesis. This study compares and evaluates a weak level of efficiency in future and spot market of gold coins.

This study examines gold coin transactions and the efficiency of future contracts in various futures and cash markets. By using the daily return of gold coins from 2008 to 2018 and R software, the paper examines the weak form of efficiency through random walks and martingale difference sequence hypotheses.

Using 10 year period data from 2008 to 2018 demonstrates inefficiency in all markets. However, compared to the other markets, the cash coin market has a relatively higher level of market efficiency. We found that there is an indirect relationship between the term of the contract and its efficiency. The weak form efficiency of the contracts is lower in the future contracts with a longer term to maturity. The probability of rejecting the weak form of efficiency is higher in futures markets.

Considering a higher level of weak efficiency in the cash market (in comparison with the future markets) and the indirect relationship between the term of the contract and the level of efficiency, investors are encouraged to focus on the gold coin cash market. Price changes in the cash market are less predictable than in other markets. As a result, this market is recommended for passive investors who buy and hold the asset.

The disposition effect refers to the tendency of selling stocks that have appreciated at price and holding stocks whose price is lower than the purchase price. Although an extensive literature has examined and confirmed the existence of the disposition effect among individual investors, there is no consensus in the literature as to whether institutional investors are also subject to similar behavioral biases or not. We test for the presence of the disposition effect among a sample of Iranian mutual funds.

We measure the disposition effect both at the aggregate and fund level, using hand-collected quarterly transactions data for a sample of Iranian mutual funds from 2010 to 2017. Our data has two unique features compared to similar studies; first, we know the exact buying price of stocks held in mutual funds' portfolios, whereas most studies need to estimate the buying price by making assumptions about purchase timing and using the prevailing market prices as a proxy. Second, unlike most studied markets, there are no capital gains taxes on the Tehran Stock Exchange and tax-motivated trading does not affect our findings.

We find that Iranian mutual funds tend to sell winning stocks more quickly than losing stocks. To be specific, the probability of selling a winning stock is approximately 1.46 times the probability that a losing stock be sold. Excluding taxes and commissions in calculating the realized profit on the sold stocks, the ratio grows to 1.51. The measured disposition effect is not driven by the effect of tax-motivated selling, since there are no capital gains taxes on the Tehran Stock Exchange. The documented disposition effect cannot be explained by funds’ internal portfolio rebalancing regulations nor by the potentially higher trading cost of selling low-priced stocks. The disposition effect exhibits a mild downward trend line throughout the sample period; however, the downward trend is not statistically significant. Partitioning the data based on the fund's portfolio value shows that both more skilled and less skilled fund managers – as proxied by fund size - are prone to the disposition effect.

Our study finds strong support for the disposition effect among mutual funds. Our results are relevant for both mutual fund managers and policy-makers.

Corporate investment in corporate financial theory is influenced by various factors, that are important in evaluating, identifying and determining the optimal level of investment of companies. Given the fact that firms often face a great deal of uncertainty about the timing, content, and potential effects of economic policy decisions, it is important to examine the implications of economic policy uncertainties. This article examines the effect of economic policy uncertainty on corporate investment in companies listed on the Tehran stock exchange during the period 2007-2020.

The studied model was estimated once with the entry of each of the variables of uncertainty resulting from inflation, interest rate, exchange rate, economic growth, monetary and fiscal policy. The uncertainty of each variable is calculated using by Hodrick-Prescott filtering. Then, the effect of economic policy uncertainty on corporate investment was investigated using GMM by introducing the composite index of economic policy uncertainty resulting from the analysis of the main components of the mentioned variables.

The results showed that the effect of the combined index of economic policy uncertainty as well as all uncertainty variables on corporate investment is negative and significant. In addition, the results showed that monetary policy uncertainty had a greater impact on corporate investment than fiscal policy uncertainty.

Economic uncertainty, by disrupting the price system, directing liquidity to financial assets and reduces the inflow of liquidity into production, reduces corporate investment. In addition, the role of monetary policy stability is more prominent due to the major dependence of firms on banking resources.

Portfolio insurance strategies are structural methods that provide a certain level of certainty by setting a floor value. In other words, using these strategies can achieve a predetermined minimum return. PI strategies, while maintaining the potential for capital growth in bull markets, provide downside protection in the bear market and at the end of the investment horizon provide a guaranteed minimum return. This study explains how to construct a portfolio and allocate assets by using these strategies, and also examines the performance of a constant proportion portfolio insurance (CPPI) strategy and value at risk based portfolio insurance (VBPI).

In order to evaluate the performance of constant proportion portfolio insurance strategy and value at risk based portfolio insurance, first the mathematical model of the Constrained Constant Proportion portfolio insurance is presented. In the Constrained case risk-free borrowing is not possible which makes the model more realistic. By using the Fourier transform of the characteristic function, the density function of returns has been extracted. By using the Density Function, the value at risk is calculated at the desired confidence levels, and finally, the mathematical model of the risk-based approach is presented. A variable-rate model is used to estimate the risk-taking movement of the asset, which is closer to reality. To estimate the dynamic of the risky asset regime-switching model has been used to make the model closer to reality.

The results show that both strategies have been successful in controlling risk, and this performance improves with increasing confidence level and frequency of portfolio rebalancing. Omega measure shows that the performance of the constant proportion portfolio insurance is better at low thresholds. Also, the dispersion of the simulated results for the final value of the portfolios showed that the constant proportion portfolio insurance works better in protecting the floor.

Portfolio insurance strategies can dramatically improve the controlling of downside risk relative to buy and hold strategy and the performance of CPPI strategy is better than VBPI according to the performance measures.

Bank-fintech collaboration scenario has become one of the new topics in the study of innovation and financial technology businesses. Yet, there has been no research into Iranian Banks collaboration scenarios as traditional financial institutions in the face of the rapid growth of fintechs that is the purpose of this research.

To develop scenarios, mixed-method research is employed. In this regard, drivers, wildcards, and weak signals of Iranian bank-fintech collaboration were listed by thematic analysis of 15 interviews of fintech ecosystem experts. Then with 33 scholars and practitioners’ participation, factors affecting collaboration were listed, successively confirmed with a one-sample t-test, and prioritized with fuzzy Topsis. Furthermore, future scenarios were developed based on Global Business Network, by distributing the questionnaire among 144 senior bank managers from 16 Iranian banks.

Legal development of fintech types and establishment of e-KYC are recognized as two key uncertainties, and subsequently the four scenarios were described: identity scenario, sine scenario, floor and ceiling scenario, and logarithm scenario. Then, private plugin services and Public API Banking Providers were proposed as robust banks’ strategies in collaboration with fintechs.

To adopt a suitable scenario and realize the robust strategies, strategic themes were identified and categorized into three areas: national governance, partnership network, and technology management. Eventually, with the expert interview, the results were confirmed.

This study is implemented to identify the factors affecting favorable financial reporting and also to investigate the impact of business and stock market cycles on the behavior of these factors.

The panel data model was used to test the assumptions of the research and the ratio of the sum of the absolute value of the effects of audit disagreement paragraphs over the absolute value of the net income was used to measure favorable financial reporting. The statistical sample of this research, after applying some restrictions, consists of 124 firms listed on the Tehran Stock Exchange from 2008 to 2017.

Research’s findings demonstrated that profitability and corporate governance quality are positively associated with favorable financial reporting; while managerial ability, audit size and firm age are not significantly associated with favorable financial reporting. The results of the Hodrick-Prescott filter showed there is no complete coincidence between boom and recession periods of business and stock market cycles during the research period. In the supplementary analysis of the research, based on the Paternoster test (1998) about the behavior of the above factors in the periods of the business and stock market cycles, audit size variable behavior influenced by the boom and recession periods of the business cycle and behavior of the profitability variable is influenced by the boom and recession periods of the stock market cycle.

The results of this study emphasize the role and importance of establishing a high-quality corporate governance system in the company and supervise the organizations concerned about its requirements. Also, in this research, favorable financial reporting is measured from an independent audit view especially based on audit standard No. 700. Lack of relationship between some factors and favorable financial reporting, which is predicted as a reflection of the high level of quality in financial reporting, on one hand, and the lack of accordance of research results with some researches results, on the other hand, may result from the lack of full compatibility of two concepts of favorable financial reporting and financial reporting quality or difference in stated variable measurement.