Packaging group Smurfit Kappa's shares dropped by 10% after announcing a merger with US company WestRock to create one of the world's largest packaging companies. The new company, Smurfit WestRock, will be headquartered in Ireland and seek a New York listing. The deal is expected to increase earnings per share for Smurfit Kappa. Despite a decline in revenue and profits, Smurfit Kappa plans to enter the US market to benefit from the rise in e-commerce.