Costly information acquisition makes it rational for investors to obtain important economic news with only limited frequency or limited accuracy. We show that this rational inattention to important news may make investors over- or underinvest. In addition, the optimal trading strategy is "myopic" with respect to future news frequency and accuracy. We find that the optimal news frequency is nonmonotonic in news accuracy and investment horizon. Furthermore, when both news frequency and news accuracy are endogenized, an investor with a higher risk aversion or a longer investment horizon chooses less frequent but more accurate periodic news updates. Copyright 2007 by The American Finance Association.

No abstract

In this paper, we show that the existence of a large, negative wealth shock and insufficient insurance against such a shock could explain both the limited stock market participation puzzle and the low-consumption-highsavings puzzle. We then conduct an empirical analysis on the relation between household portfolio choices and access to private insurance and various types of government safety nets. The empirical results demonstrate that a lack of insurance against large, negative wealth shocks is positively correlated with lower participation rates and higher saving rates. Overall, the evidence suggests an important role of insurance in household investment and savings decisions. In this paper, we use a simple model to illustrate that the existence of a large, negative wealth shock and insufficient insurance against such a shock can potentially explain both the limited stock market participation puzzle and the low-consumption-high-savings puzzle that are widely documented in the literature. We then conduct an extensive empirical analysis on the relation between household portfolio choices and access to private insurance and various types of government safety nets, including social security and unemployment insurance. The empirical results demonstrate that a lack of insurance against large, negative wealth shocks is strongly correlated with lower participation rates and higher saving rates. Overall, the evidence suggests an important role of insurance in household investment and savings decisions. Disciplines Finance | Finance and Financial ManagementJournal of Economic Literature Classification Numbers: D11, D91, G11, C61.Keywords: Limited participation, Insurance, Saving, Consumption As Campbell states in his 2006 presidential address: "Textbook financial theory implies that all households, no matter how risk averse, should hold some equities if the equity premium is positive." But, it is well documented that less than 50 percent of households in the U.S., and far less in many other countries, participate in the stock market, 1 and that this limited participation has a significant impact on the equilibrium risk premium, diversification discount, liquidity, and market crashes. 2 It is also well documented that relative to their income, households in developing countries consume less and save more than those in developed countries (Cao and Modigliani, 2004). This gap is puzzling especially given the explicit effort by governments in many developing countries to discourage saving and promote consumption as a way to reduce dependence on foreign demand for economic growth.While there exist several possible explanations for the limited participation puzzle and the low-consumption-high-savings (LCHS) puzzle, there is little overlap in these explanations.The existing explanations for limited participation rates generally rely on either transactions costs (Vissing-Jorgensen, 2002), the existence of both learning and short-sale constraints for investors whose income has a positive correlation with the stock market ...

To enable the apple picking robot to quickly and accurately detect apples under the complex background in orchards, we propose an improved You Only Look Once version 4 (YOLOv4) model and data augmentation methods. Firstly, the crawler technology is utilized to collect pertinent apple images from the Internet for labeling. For the problem of insufficient image data caused by the random occlusion between leaves, in addition to traditional data augmentation techniques, a leaf illustration data augmentation method is proposed in this paper to accomplish data augmentation. Secondly, due to the large size and calculation of the YOLOv4 model, the backbone network Cross Stage Partial Darknet53 (CSPDarknet53) of the YOLOv4 model is replaced by EfficientNet, and convolution layer (Conv2D) is added to the three outputs to further adjust and extract the features, which make the model lighter and reduce the computational complexity. Finally, the apple detection experiment is performed on 2670 expanded samples. The test results show that the EfficientNet-B0-YOLOv4 model proposed in this paper has better detection performance than YOLOv3, YOLOv4, and Faster R-CNN with ResNet, which are state-of-the-art apple detection model. The average values of Recall, Precision, and F1 reach 97.43%, 95.52%, and 96.54% respectively, the average detection time per frame of the model is 0.338 s, which proves that the proposed method can be well applied in the vision system of picking robots in the apple industry.

No abstract

Contrary to the prediction of the standard portfolio diversification theory, many investors place a large fraction of their stock investment in a small number of stocks. I show that underdiversification may be caused by solvency requirements. My model predicts that for quite general preferences and return distributions: (1) underdiversification decreases in discretionary wealth; and (2) expected return and covariance determine which stocks to invest in, but variance, higher moments, and Sharpe ratio do not matter for this choice. In addition, a less-diversified stock portfolio has a higher expected return, a higher volatility, and a higher skewness, and idiosyncratic risks are priced.

M ost existing portfolio choice models ignore the prevalent periodic market closure and the fact that market volatility is significantly higher during trading periods. We find that market closure and the volatility difference across trading and nontrading periods significantly change optimal trading strategies. In addition, we demonstrate numerically that transaction costs can have a first-order effect on liquidity premia that is largely comparable to empirical findings. Moreover, this effect on liquidity premia increases in the volatility difference, which is supported by our empirical analysis.

No abstract