I just read a literature review (sorry, don't have the reference) of types of compression garment (kneesocks vs thigh-high vs abdominal compression vs everything at once) which showed (although the studies were hard to compare) that abdominal compression works best, with the presumption being that this is because it's splanchic pooling that's a big player for most people like Sushi says.
I have compression tights that come up to my waist, prescribed by my doctor, but haven't found them to be of any benefit on their own. However, a store-bought corset (!) does have some effect for me and is considerably more tolerable than the tights, which are extremely difficult to get on, extremely hot, and pull themselves down because of the tension in them (they will pull a pair of jeans down if I wear them underneath so needless to say, I can't go out in them!).