I haven't yet found statistics on the relationship between Open Carry and crime prevention or propulsion, but I have found definitive study on public and professional perception regarding those who carry a handgun openly. Most notably, the 2006 FBI study "Violent Encounters: A Study of Felonious Assaults on Our Nation's Law Enforcement Officers" by Anthony Pinizzotto revealed that criminals carefully conceal their firearms, and they eschew the use of holsters. In other words, those who openly subject themselves to the public scrutiny and misconception are likely, and statistically proven to not be criminals or have criminal intentions in mind when carrying a weapon.
Unfortunately, I now live in Tennessee where I have to apply for a permit to exercise my natural born right of self preservation, and I have yet to follow the herd into that realm. However, I used to live Kentucky where I could open carry as I please and I did apply for and receive a concealed carry permit. I often Open Carried and on one particular occasion I was exiting my vehicle to fill my tank at the pumps of a local gas station when I noticed a man putting on a second-chance vest in his car (light military armor that gives wearer a "second chance" if they happen to encounter shrapnel; not bulletproof). This struck me as odd and although I hadn't originally thought to go inside (paying at the pump) I started filling my tank and cautiously walked towards the store entrance. As I was walking up, my Ruger P90 .45 was on my right hip, clearly visible to the gentleman with the vest who was also walking to the front door from my right. I made eye contact with him, watched him glance down at my pistol and immediately saw his stride and facial expressions change. He continued in the store and went directly to the bathroom; I stayed out in the aisles waiting for him to exit the bathroom. After 2 minutes passed, I saw him Turkey peak out of the bathroom and this time my Military bearing was in full swing. I was fully confident about what I had to do next if the situation were to escalate, and I was prepared. He then walked out in full view, and immediately saw me next to the chip racks: deer in the headlights look! His color changed to a pale-white and I made an ever-so-slight head gesture to the left, signifying that he could leave unharmed, if he'd just leave. He didn't pick up anything for purchase. He didn't look around. He hurriedly walked out of the store, jumped in his car and left the store.
Did I divert a potential threat? Did I stop a robbery? I don't know and there will never be a statistic on that because we never let it play out. But I am confident that the mere presence of not only my weapon, but also of my confidence to use it stopped that man from doing something stupid. I'll never know if he had a gun, but I know what a second chance vest is from my time as a Marine Corps Tank Crewman, and that was unmistakable. Since that day, I have carried my Pistol with me everywhere I go and I pray that I get a chance to use it in exactly that same manner; as a preventative device designed to thwart evil doings. Statistically, I would say that there are a larger number of incidents like mine unreported v. reported. So if your wife is looking for evidence, tell her to read my story.