If the two pandas have a cub, the new contract states the Memphis Zoo does not have to pay China a yearly fee on that. However, the cub will have to be returned to China after four years.
Panel study. A panel study is a longitudinal study design where a cross-sectional sample of units is selected and surveyed at usually regular intervals. The observation units may be individuals, households, firms or other organisations, or even countries. Household panel surveys are an important sub-type of panel study.
What is a Cohort? The focus of a panel study is a group of people who have a common attribute, experience or characteristic in a particular time period. This group is called the cohort. People that share the fact of being born on the same day, month, year or era may belong to a birth cohort.