“Reduced odds of surgery were observed for…those whose first provider was a chiropractor. 42.7% of workers [with back injuries] who first saw a surgeon had surgery, in contrast to only 1.5% of those who saw a chiropractor.” (6)
“Cervical spine manipulation was associated with significant improvement in headache outcomes in trials involving patients with neck pain and/or neck dysfunction and headache.” (12)
“Many treatments are available for low back pain. Often exercises and physical therapy can help. Some people benefit from chiropractic therapy or acupuncture.” (13)
You can find more research here that includes information on the following: public opinion, reduction in costs, outcomes and efficacy, and prevalence.