Disasters can happen all over the world. They are unpredictable and now part of people's lives (Zhang and Huang 2018). Evidence shows that the number of disasters is increasing dramatically and is about to increase five times in the next 50 years (Mahdavi et al. 2015). In the last twenty years, more than 1.3 million people have lost their lives and 4.4 billion people were injured, rendered homeless, displaced, or in need of emergency assistance. During this period, disaster-hit countries reported direct economic losses of $2.9 trillion US which climate-related disasters accounted for 77% of the total. The last twenty years have seen a dramatic rise of 151% in direct economic losses from climate-related disasters(CRED and UNISDR 2018).
When a disaster happens, immediate emergency responses are needed to save lives and relieve and control the damages. Hence various resources and equipment are utilized in the relief logistics process to effectively manage the crisis and provide the necessary relief commodities to the affected people (Lu et al. 2016). These resources include organizing and sending the health care workforce to provide relief, health care, and necessities of life for the injured, including tents, blankets, clothing, living and food supplies, and financial resources such as loans and grants to start and complete the reconstruction (Melis and Jean 2021).
Relief logistics (also known as logistics of relief materials) is the most efficient intervention operation and yet one of the most challenging issues in emergency response to disasters (Liu et al. 2018). The problem here is that relief logistics operate in environments with uncertain and dynamic features (both in the supply side and demand side), and the precise relief demands are particularly complicated to determine due to the uncertainties (Zhan and Liu 2016). Furthermore, disaster relief demand is specifically hard to quantify because the magnitude, location, and timing of disasters can be highly unpredictable (Ozdamar 2017). Nevertheless, research suggests the amount of relief supplies required to satisfy the demands of disaster victims especially in low and lower-middle-income countries is significantly higher than preliminary estimates (Falasca and Zobel 2011, Khankeh et al. 2011, Afshar and Haghani 2012). Therefore, the governments have to spend most of the financial resources provided to disaster response management to meet the demand for relief to the affected people, and disaster relief logistics has emerged as a theme of their concern since the available funds are restricted and should be used optimally (Gossler et al. 2019).
According to recent studies, humanitarian and rescue organizations spend billions of dollars each year to help victims of disasters (Bastos et al. 2014, Chang et al. 2011, Gossler et al. 2019). In 2017, an amount of $27.3 billion US was allocated to the international humanitarian response . In this context, it is notable that relief logistics account for a considerable proportion (up to 80 percent) of disaster relief costs and tasks (Hein et al. 2020). For example, after the Tohoku crisis in 2011, which caused $ 360 billion in financial loss, the Japanese government spend more on economic and public support for affected people than on reconstruction of the public infrastructure (Authors 2017). Remarkably meeting the needs of the affected people through logistics processes is the most costly part of disaster response operations, which, if conducted properly, can save resources and improve the quality of care and ultimately reduce economic and social problems (Schulz 2009). Furthermore, relief overdemanding in the disaster response often leads to massive emissions and accumulation and waste of surplus resources in the affected area. The lesson learned from Bam earthquake management confirmed that the attendance of more than enough staff of rescue organizations and volunteers in the affected area was a great challenge of disaster management so that providing daily necessities for these people was a big concern for local managers (Khankeh et al. 2011). However, appropriate delivery of relief resources to disaster victims is critical to the emergency response to disasters. Although some other works address the relief uncertainty and several problems related to relief logistics have been discussed (Sheu and Pan 2015, Lin et al. 2020), unfortunately, literature in relief demanding is very limited, and factors associated with the relief overdemanding are not studied yet. Therefore, this study was conducted to investigate the reasons for relief overdemanding after the occurrence of disasters.