Because compression dimensions are dynamically calculated, you must take into account design considerations for dynamically calculated dimensions when choosing a compression dimension. Dynamic dimensions are calculated at the time of retrieval, so the data retrieval time is longer than for stored hierarchies.
If a dimension with a large number of level 0 members is tagged as compression, upper-level queries take longer because they require many level 0 members to be retrieved. If users will be doing many upper-level retrievals on a large dimension, it is not a good candidate for a compression dimension.