Serious Eats - seriouseats.com

@JerzeeTomato: (I don't mean to stir the waters here, but this chain of comments made me curious so I just had to do the calculations...err, I'm a nerd?) I'm afraid I must actually agree with pthom, it doesn't inherently make sense that the carbohydrate content of a foodstuff would decrease during the process. Of course, I'm no expert on the manufacturing process of instant mashed potatoes, so who knows, maybe some of the starch is leached as a step in the process?

Anyways, let's take a look at the numbers based on the two sources you cited; the basic problem is that the two sites list the nutritional information using differing units of measurement, and the two cannot be compared directly. Thankfully though, the Idahoan site also gives the serving size in grams. w00t! Thus we can calculate:

Real potatoes: 23 g Carbs / 150 g Potato = 0.153 g Carbs / g Potato

Idahoan potatoes: 18 g Carbs / 23 g Potatoes (using the unprepared serving measure; this is equal to the 1/2 cup cooked serving size) = 0.782 g Carbs / g Potato

From this, we can clearly see that the Idahoan potatoes actually have nearly 5 times more carbs per a given serving size than 'real' potatoes....or at least, based on the sources you gave. Since it looks like you also found info somewhere that 4 oz baked potatoes have much more carbs than the Idahoan, I think the only real conclusion we can make is that nutritional information really seems to vary!

(If we do the same calculation for a baked potato, using the info given on the mvproduce site, then it turns out that a baking potato actually has even less carbs per gram potato than a regular potato! That would be:

(23 g Carbs *1.6) / 250 g Baking Potato = 0.1472 g Carbs / g baking potato )