How much does 1 teaspoon of fresh ginger equal to ground ginger?

Sources vary. One source says 1 tbsp fresh equals 1/4 tsp ground, another says 1 tbsp fresh equals 1/8 tsp ground (half as much!). So I translate them to either 1/12 tsp of ground or even less (because there are three teaspoons in a tablespoon). How about a few shakes from the jar? That's what I do when the recipe says one teaspoon freshly ground and it hasn't ruined anything yet.