**1. Introduction**

Sustainable investing has received interests from both public and private sectors around the world for decades. Generally, it refers to the investment processes that integrate investing with factors that are perceived to have positive impacts to the environment, to the societies, and to the world at large. These factors are often referred to as the environmental, social, and governance (ESG) factors. In addition, companies around the world have paid a significant focus on creating activities and investment decisions that meet these objectives. The ESG activities have often been measured and cited in the companies' annual reports. Not only that, several stock indexes are also commonly constructed relative to the ESG ratings, for example, the S&P 500 ESG Index, while constructed similarly to the S&P 500 Index, is an index designed to measure the performance of securities that meet the ESG criteria. The number of companies that report ESG data has also increased significantly. According to Amir

and Serafeim [1], there were fewer than 20 companies that reported ESG data in the 1990s. On the other hand, there were about 9000 companies that issued and reported sustainability and ESG data in 2016. Using survey data, they found that the most frequent motivation as to why ESG information was used was related to investment performance, followed by client demand, product strategy, and ethical consideration, respectively. ESG market size has also expanded tremendously as well. Bloomberg reported on July 21, 2021 that ESG assets are on track to exceed \$50 trillion by 2025, which will represent more than a third of total global asset under management. The implications and contributions of ESG investment have widely been examined. However, the consensus regarding the advantages and disadvantages of ESG investing has yet been reached. In this chapter, we will explore the ESG investment and its implications in several dimensions, by reviewing literature related to the relationship between ESG information and firm performance. Possible areas that lead to the inconclusive of the ESG effects on investments will also be discussed, along with the direction of future studies that should advance the studies in this area.

The rest of the chapter is organized as follows. Section 2 presents the relevant ESG investment literature. Section 3 discusses the inconsistencies in examining the impacts of ESG investments. Section 4 concludes.
