seekers, and led many European governments to require Gambians to have a visa before traveling. Faced with more restrictive immigration policies, many Gambians wishing to migrate increasingly turned to irregular migration.

This irregular migration typically takes place through what is known as the “backway”, which involves travel overland through the Sahara Desert, through Morocco or Libya, and then across the Mediterranean Sea to Spain or Italy. Each stage of this journey involves many dangers. Travel through the Sahara Desert typically takes place in crowded open trucks (from which migrants often fall and are left behind to die) to get to Libya, where they face a variety of serious challenges, including abductions for ransom, slavery, torture and other ill-treatments.<sup>8</sup> Considering the additional risks of drowning in the Mediterranean, having the smuggler boat caught and being brought back to Libya,<sup>9</sup> and being deported upon arrival in Europe,<sup>10</sup> results in an estimated overall 4% success rate of attempted backway migration journeys.<sup>11</sup> Despite these risks, the irregular emigration rate from The Gambia to Europe grew substantially in the first half of the 2010s. These trends can be seen in data from the European border agency, Frontex, shown in Figure 1.<sup>12</sup> Recorded irregular migration flows from The Gambia grew from 8 Numbers on the death rates of irregular migration from West Arica to Italy through the Central Mediterranean route are very scarce and hence have limited reliability. According to our calculations combining the evidence collected by the North Africa Mixed Migration Hub (MHub) with the existing numbers on death rates in the Mediterranean, 22% of those attempting to cross the Saharan desert and other transit countries to reach Libya died in the process. Of those who reached Libya successfully, another 23% died mostly due to physical violence. <u>http://www.mixedmigrationhub.org/wp-content/uploads/2017/02/Italy-MHub-Survey-Snapshot-Jan-2017.pdf</u> [Last accessed on July 23, 2019.] 9 Respectively 7.6% and 46.7% of crossing attempts, according to a report by the Washington Post: <u>https://www.washingtonpost.com/world/europe/fewer-migrants-are-making-it-to-europe-hereswhy/2018/07/23/80b56082-8c57-11e8-9d59-dccc2c0cabcf_story.html?utm_term=.b55d2511d50e</u> [Last accessed on July 23, 2019.] 10 According to the Eurostat, in 2017 the probability of being deported upon irregular arrival to Italy from The Gambia was 57.6%. However, this deportation rate increased very strongly, reaching 86.6% in the last quarter of 2018, according to the Eurostat. These updated numbers were used as a component of the information and deterrence intervention we implemented.

11 The 4% success rate is a lower bound that we used in the absence of information on multiple Mediterranean crossing attempts. Note that even if migrants attempted to cross the Mediterranean one more time after being brought back to Libya, their overall success rate would still be only 5%.

12 As mentioned before, Frontex numbers may not be capturing all irregular migration, since those who are not intercepted or do not claim asylum status will not be recorded in any statistics. However, while the levels may be an undercount, we believe the trends are informative. In Bah et al. (2021), we use retrospective questions on migration 9