Ritmos sensoriomotores (ritmos mu y beta)

There is a growing interest in literature that explores the relations between terrorist attacks and stock markets, particularly after 9/11. Prior studies have shown that terrorist attacks increase financial instability and weaken investor confidence (Abadie & Gardeazabel, 2003; Johnston & Nedelescu, 2005; Lenain et al., 2002), and have attracted attention as a business risk to be considered by investors in decision-making (Jain & Grosse, 2009; Luo, 2009). Asset pricing theory implies that when bad news arrives, expected future asset values decrease.

Consistent with asset pricing theory, the literature has shown that terrorist attacks lead to negative stock returns around the day of the attacks (e.g., Balcilar, Gupta, Pierdzioch, & Wohar, 2018; Drakos, 2010; Eldor & Melnick, 2004; Karolyi & Martell, 2010; Ramiah, Cam, Calabro,

Maher, & Ghafouri, 2010). Abadie and Gardeazabel (2003) show that when the Basque ETA declared a ceasefire between 1998 and 1999, a sample of Basque stocks generated abnormal returns vis-à-vis non-Basque stocks on 22 trading days characterized by good news (indicating that the truce was credible), whereas after the ceasefire, Basque stocks significantly underperformed their counterparts in 66 days of trading. Eldor and Melnick (2004) examine the impact of terrorist attacks on Israeli financial markets. Their results suggest that terrorist attacks depress stock indices and reduce firms’ expected profit. The Israeli stock market lost 30% of its value during 2000–2003 as a result of the intensification of the Israeli–Palestinian conflict. Karolyi and Martell (2010) find that terrorist attacks pose significant negative shocks to stock prices around the day of the attacks and this effect is more pronounced when the attacks occur in more democratic and developed countries.

A stream of research explores the contagion effect that terrorism has in stock markets. Nikkinen, Omran, Sahlström, and Äijö (2008) examines the impact of 9/11 on 53 equity markets. Their results indicate 9/11 significantly increased market volatility across regions and led to significant negative returns in the short run, which quickly recovered afterwards. The level of impact depends on the degree to which the region is integrated with the global market. Less integrated regions, such as the Middle East and North Africa, are less influenced by the shock. Similarly, Bilson, Brailsford, Hallett, and Shi (2012) suggest that 9/11 induced substantial contagion consequences, in particular, for equity markets in developed countries. S. Narayan et al. (2018) examine whether exposure to terrorism risk influences stock market integration among eight OECD countries for the period 2001–2014. Their result suggest that in Australia, U.K., Germany and Turkey, terrorism risk is positively associated with the level of market integration, indicating the contagion effects of terrorism. By contrast, higher terrorism risk

The literature also suggests that the impact of terrorism can be more pronounced in specific industries. Carter and Simkins (2004) examine the stock price reaction of firms in the air transport industry in the aftermath of 9/11, in light of market concerns of heightened risk with respect to these stocks. They found that on the first trading day after the 9/11 attacks, airline stocks were “pummelled” and there were larger and more significant abnormal returns for U.S. airlines than international airlines and airfreight firms. Ramiah et al. (2010) document significant short-term negative abnormal returns in the Australian market around 9/11, the 2004 Madrid bombings and 2005 London Bombings. The impact was particular large in the utilities sector, where industry return fell by 37.3% on the day of 9/11. Chesney et al. (2011) explore the impact of 77 terrorist events on stocks, bonds and commodities and found that two-thirds of terrorist attacks impose significant negative impacts on at least one stock market globally, primarily on the event day. They found that the insurance, travel and airline industries were most affected for global bond markets,32 _{and reacted negatively both on the event day and in}

the short-term period examined thereafter.

Drakos (2010) examines the impact of terror activities on stock returns using terrorist attacks as mood indicators. Edmans, Garcia, and Norli (2007) suggest that markets can be influenced by sentiment variables if such variables 1) drive the mood in a substantial and unambiguous manner so that their effect is powerful enough to show up in asset prices, 2) affect the mood of a large proportion of the population so that investors are likely to be affected as well, and 3) have effects that are correlated across the majority of individuals within a country. Terrorist attacks satisfy these three criteria. Targeted countries were left in shock, fear and anger after the attacks. Terrorism incidents may be seen as signs of future attacks elsewhere, thus leading to responses that have immense psychological, socioeconomic and psychosocial impact. Using

a sample of stock market indices for 22 countries for 1994–2004, Drakos shows that terrorist activity leads to significantly lower returns on the day a terrorist attack occurs and the negative effect of terrorist attacks is substantially amplified when the attacks cause higher psychosocial impact.

Terrorist attacks have also been found to increase stock return volatility (e.g., Arin, Ciferri, & Spagnolo, 2008; Balcilar et al., 2018; Essaddam & Karagianis, 2014; Kollias et al., 2012). Arin et al. (2008) suggest that terrorism threats lead to greater volatility in stock markets based on evidence from six countries. Kollias et al. (2012) show the 2005 London Bombing increased volatility of stock market returns on the London Stock Exchange and the effect was also transmitted to the Frankfurt and Paris stock exchanges. Essaddam and Karagianis (2014) found that stock volatility increases on the day of terrorist attack and can remain significantly high for at least 15 days following the day of the attack. Overall, these studies show that terrorist attacks create negative shocks to stock markets, which lead to negative stock returns and greater volatility. Balcilar et al. (2018) test the effects of terror attacks on stock market returns and volatility in G7 countries, and suggest that terror attacks often have significant effects on returns, and significantly increase market volatility for Japan and the U.K.

Prior research also suggests that the impact of terrorist attacks on equity prices is typically transitory (e.g., Kollias et al. 2011a, 2011b). It has been argued that financial markets are able to recover more quickly from terrorist attacks after 9/11 (Chen & Siems, 2004; Kolias et al., 2011b; Ramiah et al., 2010) and markets as a whole are “fairly insensitive to the major terrorist attacks post September 2001” (Ramiah, 2010, p. 66). For example, Kollias et al. (2011b) found that the London Stock Exchange recovered within one trading day from the 2005 London