How many animals die every 12 years due to animal testing?

Estimates say that anually; 60 to 100 million veribrate animals worldwide are being used for testing. 70% of these are mice or rats. Most animals are used in only one procedure: animals either die because of the experiment or are euthanized afterwards. Scientists and governments state that animal testing should cause as little suffering to animals as possible, and that animal tests should only be performed where necessary. Although such principles have been welcomed as a step forwards by some animal welfare groups, they have also been criticized as both outdated by current research, and of little practical effect in improving animal welfare.