I have created a calculated measure through BIDS in a SSAS cube and it's like the following:

```
IIF([Measures].[RatePct] >= 0.90, [Measures].[measureA], [Measures].[measureB])
```

The point is that if I convert the above to this:

```
IIF([Measures].[RatePct] >= 0.90, [Measures].[measureA], 0)
```

or that:

```
IIF([Measures].[RatePct] >= 0.90, [Measures].[measureA] + 100, [Measures].[measureB])
```

the measure becomes extremely slow when using it in the cube.

Any ideas why this is happening and how can it be addressed?

Many thanks