Explosivity and Time-Varying Granger Causality: Evidence from the Bubble Contagion Effect of COVID-19-Induced Uncertainty on Manufacturing Job Postings in the United States

This study evaluates the explosive behavior and Granger causality episodes in manufacturing job postings in the United States (JOBPUS) and COVID-19-induced uncertainty (COVIDEMV). This study applied the novel unit root tests with explosive behavior, and the novel time-varying Granger causality test for a sample period ranging from 1 January 2020 to 29 July 2022. Further, this study used date stamping to identify the subperiods of the explosive behavior and causality. The findings revealed that JOBPUS exhibits explosive behavior, with several episodes of exuberance (bubbles) across the sample period while COVIDEMV does not exhibit explosivity during the period. However, the results of the causality provide evidence of bidirectional causality, with several episodes between the variables. Moreover, the episodes of the explosivity and causality coincide with significant episodes in the history of the COVID-19 pandemic worldwide and in the United States particularly, such as the date when United States recorded a COVID-19-related death toll of over 100,000 people for the first time, after the presidential election, after Halloween celebrations, after the discovery and administration of COVID-19 vaccines as well as the discovery of the Delta and the Omicron variants of COVID-19. Therefore, the time-series characteristics of JOBPUS and its causal nexus with COVIDEMV largely depend on the intensity of the instability caused by the pandemics. Hence, explosivity and time-varying causal behavior should necessarily be accounted for when modelling the job market conditions in the United States, particularly during pandemic-related crises.