Take a class tally on how many brothers or sisters each pupil has. Show this as a histogram on the board (prepare a graph template using spreadsheet software beforehand). Ask them how the results of this activity might have been different for their parents and for their grandparents. Ask pupils to list the reasons why Jill has chosen to have fewer children than her ancestors, and then ask them to think of more reasons. Why do some people in some parts of the world have more than two children? What will happen if more women took Jill's decision?