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AbstractThis paper analyzes the relationship between volatility and risk premium under the capital asset pricing model and Rothschild and Stiglitz's [Rothschild, M. and J.E. Stiglitz. (1970) Increasing risk I: a definition. Journal of Economic Theory, 2, 225–243.] definition of increasing risk. Especially examined are the conditions of the widely used assumption of constant correlation, which results in a linear relationship. Though both the above model and definition are widely known and accepted, their compatibility has remained unclear in the literature. According to this paper, they are in harmony with the linear relationship, if the correlation between a stock and the market portfolio is less than 0.7. Otherwise a conflict may arise.

AbstractThe complex networks approach has been gaining popularity in analysing investor behaviour and stock markets, but within this approach, initial public offerings (IPOs) have barely been explored. We fill this gap in the literature by analysing investor clusters in the first two years after the IPO filing in the Helsinki Stock Exchange by using a statistically validated network method to infer investor links based on the co-occurrences of investors' trade timing for 69 IPO stocks. Our findings show that a rather large part of statistically similar network structures form in different securities and persist in time for mature and IPO companies. We also find evidence of institutional herding.