All pot that is grown, with a few exceptions, comes in ratios of the above two. So for example, one strain may be 50% Indica and 50% Sativa... when you first smoke it, you will feel the heady, creative high, but as the effects wear off, it will fade into a dull, stoner high. The strains I grew and preferred were at least 80% sativa.
The vast, vast majority of pot that is distributed on the streets and through private dealers is predominantly indica. This is because the indica sub-species is smaller in size (for hiding), grows from seed to harvest in a shorter period of time, and the yield is usually higher. Sativas grow taller so they are harder to conceal in larger scale grow-ops, and they take longer to grow to maturity. Also, the best sativa varieties are outdoor ones which grow significantly larger, and anywhere that pot has illegal status makes it difficult to do this way.
So, as a result, most private growers who do grow sativas keep the harvest for themselves, as it is a far superior variety. They save the indica stuff for the streets because it is more suitable for mass production. Unfortunately, this also cheapens the effects for many, many people.