People are more willing to bet on their own judgments when they feel skillful or knowledgeable (Heath and Tversky (1991)). We investigate whether this "competence effect" influences trading frequency and home bias. We find that investors who feel competent trade more often and have a more internationally diversified portfolio. We also find that male investors, and investors with higher income or more education, are more likely to perceive themselves as competent investors than are female investors, and investors with lower income or less education. Our results are unlikely to be explained by other hypotheses, such as overconfidence or information advantage. Finally, we separately establish a link between optimism towards the home market and international portfolio diversification.

People are more willing to bet on their own judgments when they feel skillful or knowledgeable. We investigate whether this "competence effect" influences trading frequency and home bias. We find that investors who feel competent trade more often and have more internationally diversified portfolios. We also find that male investors, and investors with larger portfolios or more education, are more likely to perceive themselves as competent than are female investors, and investors with smaller portfolios or less education. Our paper also contributes to understanding the theoretical link between overconfidence and trading frequency. Existing theories on trading frequency have focused on one aspect of overconfidence, i.e., miscalibration. Our paper offers a potential mechanism for the "better-than-average" aspect of overconfidence to influence trading frequency. In the context of our paper, overconfident investors tend to perceive themselves to be more competent, and thus are more willing to act on their beliefs, leading to higher trading frequency.

Aging is a complex process (or series of processes). Recent evidence suggests that several of its most important mechanisms are linked by means of cellular damage caused by reactive oxygen species (ROS). Oxidative damage may be a major factor in the loss of physiological functions that occur in degenerative diseases and aging. This is because, in aerobic organisms, the mitochondrial electron transport chain plays an important role in energy production and is a significant source of ROS that damage DNA, RNA, and proteins in cells. While oxidative events in other cell organelles are likely to contribute to the pathobiology of aging, this review highlights alterations in mitochondrial function that, due to accumulated oxidative damage, occur with age.

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Aging is characterized by a proinflammatory state that contributes to the onset of disability and age-related diseases. Proinflammatory cytokines play a central role in mediating cellular and physiological responses. The levels of these cytokines may reflect immune system effectiveness. Studies of the effects of aging on inflammatory response show interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) to be important. In this review, age-related changes in inflammatory cytokines, T and NK cells, and the biology of IL-6 and TNF-alpha and their relevance to senescence are considered.