This article, and many more on "Stand Your Ground" are total BS.

First of all, the Zimmerman/Martin case that has fueled all this attention was never a valid example of "SYG" in use as Zimmerman only resorted to lethal force when he had no way to retreat and was having deadly force used against him, and even then based on the recorded cries for help, he hesitated before employing lethal force and the level of force employed was restrained (one shot was fired when he could have fired 5+ times).

Secondly the basis of "duty to retreat" from English Common Law is specific to cases such as a brawl or simple assault which does not excuse homicide in self-defense except when "but in sudden and violent cases; when certain and immediate suffering would be the consequence of waiting for the assistance of the law":

From Repuiblic Study Guide - Training Material Search Results
2. HOMICIDE in self-defense, or se defendendo , upon a sudden affray, is also excusable rather than justifiable, by the English law. This species of self-defense must be distinguished from that just now mentioned, as calculated to hinder the perpetration of a capital crime; which is not only a matter of excuse, but of justification. But the self-defense, which we are now speaking of, is that whereby a man may protect himself from an assault, or the like, in the course of a sudden brawl or quarrel, by killing him who assaults him. And this is what the law expresses by the word chance-medley , or (as some rather choose to write it) chaud-medley ; the former of which in its etymology signifies a casual affray, the latter an affray in the heat of blood or passion: both of them of pretty much the same import; but the former is in common speech too often erroneously applied to any manner of homicide by misadventure; whereas it appears by the statute 24 Hen. VIII. c. 5. and our ancient books,35 that it is properly applied to such killing, as happens in self-defense upon a sudden reencounter.36 This right of natural defense does not imply a right of attacking: for, instead of attacking one another for injuries past or impending, men need only have recourse to the proper tribunals of justice. They cannot therefore legally exercise this right of preventive defense, but in sudden and violent cases; when certain and immediate suffering would be the consequence of waiting for the assistance of the law. Wherefore, to excuse homicide by the plea of self-defense, it must appear that the slayer had no other possible means of escaping from his assailant.

Thirdly, failing to categorize the "study" results by "justifiable" or "non-justifiable" homicides shows clear bias.
I have read other articles about this "study" from Texas A&M and it specifically states that "castle doctrine laws increase the narrowly defined category of justifiable homicides by private citizens by 17 to 50 percent" while "the laws increase murder and manslaughter by a statistically significant 7 to 9 percent" which sounds to me like the good outweighs the bad, and many cases in that 7 to 9 percent are likely cases that would otherwise have been found as justifiable except that the "defender" was either engaged in criminal activity or not in a place where his legal right to be was covered under SYG laws.