Early in the 1990s, the developed countries of the world began phasing out the production of chlorofluorocarbons (CFCs), a group of chemicals believed to be responsible for the destruction of stratospheric ozone. By 1996, all production of CFCs by developed countries had ceased.

This graph shows the minimum levels of ozone over Antarctica through the year 2000. The number above each red dot is the observed ozone level (in Dobson units), and the number below the dot (e.g. 9/30) is the month and day of that reading.

12. How does the graph of minimum ozone levels in the late 1990s compare to the graph of levels before that time?