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A debt contract promises a creditor a fixed repayment not contingent on a debtor’s performance. At the same time, it provides the creditor with a right to foreclose on the debtor’s assets in default and to enforce liquidation. However, in practice, even when the debtor misses (i.e., defaults on) the promised repayment, the creditor does not always enforce liquidation. Instead of enforcing it, she occasionally permits the defaulting debtor to restructure the contract terms to obtain relief (forgiveness) from the liability. The agents continue to keep the contractual relationship beyond the default.
Sexual dimorphism, particularly sexual size dimorphism has been observed in a large number of animal taxa (Shine 1989, Blanckenhorn 2005). Two main hypotheses, both first suggested by Darwin in 1874, have been proposed to explain the evolution of sexual size dimorphism. The first hypothesis proposes that sexual selection causes the observed differences and predicts that the relationship between body size and reproductive success differs between sexes. The result is selection favouring different body sizes at adulthood. This has proven to be an easily testable prediction and has been explored in many animal groups (reviewed by Andersson 1994 as cited by Pearson 2002). Among the most common examples is the degree to which males are larger than females in mating systems that involve male-male combat. There exists an important correlation between the intensity of male-male combat and the degree to which males exceed females in adult body size (e.g. Trivers 1976).
The second hypothesis proposes that ecological causes play an important role in the evolution of sexual size dimorphism, which may lead to sexes exploiting different ecological niches (Slatkin 1984, Shine 1989). Since ecological niches are often difficult to describe, Shine (1989) proposed the use of trophic structures (e.g. jaw width or length) as a tool to compare niche partitioning between sexes. If niche divergence has occurred, particularly through diet specialization, sexual differences in trophic structures may be a good indicator of specialization. When these structures are not sexually selected they become good candidates to test this hypothesis. Furthermore, to eliminate the simple effect of larger body sizes between the sexes, it is also important for trophic structures to be more dimorphic than body size (Shine 1989, 1991, Thom et al. 2004). Using these parameters, much evidence for the ecological causes of sexual size dimorphism has been put forth (see e.g. Shine 1991, Temeles et al. 2000, Shetty and Shine 2001, Pearson et al. 2002, Thom 2004). Snakes have been used as a particularly good example of this phenomenon since they are gape-limited predators and maximum ingestible prey size is limited by the size of the snake’s head (Shine 1991).
According to Fama [1970] even if financial markets are not able to fulfil all the sufficient conditions which are implied by the informational efficiency hypothesis, still it is possible to state its efficiency due to fair game model. The three forms of informational efficiency defined by Fama (weak, semi-strong and strong) could be considered as different levels of investors’ ability to correctly valuate shares. In consistence with Fama theory [1976], in an efficient market the true expected return on any security is equal with its equilibrium expected value. At this time, Fama’s theory on informational efficiency represents, at least for emergent capital markets, a “corner-stone” for any discussion about shares pricing. Informational efficiency hypothesis does not recommend a model for stocks’ price evaluation, but reveals investors’ ability to evaluate stocks in a proper manner. Fama [1970] presented various empirical tests, which had been previously performed in order to analyze the possibility of obtaining abnormal returns due to historical information about stocks, or due to publicly available or private information affecting them (serial correlation, distributional evidence, events studies). Several years after, Fama [1991] reviewed his 1970 work and classified empirical tests of market efficiency in the following categories: (i) tests for return predictability; (ii) event studies; (iii) tests for private information, which follow the three forms of informational efficiency. Megginson [1997] completed Fama’s classification with tests for rational fundamental valuation.
Most of the studies in Finance referring market informational efficiency hypothesis, express that it could be empirically tested by using some econometric methods based on random walk movements of returns. The significance of such tests is that investors could not forecast future returns of assets, if they follow a random walk. If the future price is not predictable, these tests confirm that each condition implied that no one could obtain abnormal returns is fulfilled. Practically, this statement represents the main stream in Finance literature (Megginson, 1997).
