Matt Allington shows how that reducing cardinality helps with reducing data sizes with DAX:
With both of these concepts combined, the file size was reduced from the original 264 MB to 238 MB, a reduction of almost 10%. You can see where the space savings have come from by comparing the before and after column sizes in the 2 tables below. The SalesValueExTax column (65MB) was replaced with the Margin column (44MB) and the CostValue column (63MB) was replaced with the CostPerCase column (50MB).
Check it out, as well as the memory tool.