This is from the Wisc DNR "fact Sheet" on wolves......
A few hunters continue to illegally kill wolves, believing that such actions will help the deer herd. It is important to place in perspective the impact of wolves preying on deer. Each wolf kills about 20 deer per year. Multiply this by the number of wolves found in Wisconsin in recent years (800), and approximately 16,000 deer may be consumed by wolves annually. This compares to about 27,000 deer hit by cars each year, and about 340,000 deer shot annually by hunters statewide. Within the northern and central forests where most wolves live, wolves kill similar numbers of deer as are killed by vehicles (about 8,000), and about 1/10 of those killed by hunters (8,000 in 2010). Wolves are a factor in the deer herd, but only one of many factors that affects the total number of deer on the landscape.