Okay, so when you are referring to the time period of the data, use the past tense. For example, “People in the Uk in 2004 ate 2 million tonnes of chicken”
*However, it you are referring to the graph (which shows information in the present) make sure to use present tense. Ex. The graphs shows that people in the UK eat 2 million tonnes of chicken in 2005.
Keep up the good studies.