Why is planning and forecasting a global workforce so difficult?

Please respond to the following Discussion Board questions for week 3 after considering assigned textbook reading, articles, etc.Why is planning and forecasting a global workforce so difficult? What are some approaches/tools that might be helpful from a global HR perspective? What were some of your key takeaways from the Cummins video example?What factors should Global HR take into consideration when evaluating various MNE staffing strategies?