Instruction execution throughput increases in proportion with the number of pipeline stages.

This statement is not necessarily true. While it's true that pipelining can increase instruction execution throughput by allowing multiple instructions to be in different stages of execution simultaneously, simply increasing the number of pipeline stages doesn't always lead to a proportional increase in throughput.

Here's why:

1. Pipeline Hazards: These are situations that prevent the next instruction in the instruction stream from executing in the ideal cycle. There are three types of hazards: data, structural, and control hazards. Increasing the number of pipeline stages can increase the likelihood of these hazards, which can stall the pipeline and decrease throughput.

2. Pipeline Overhead: Each stage of a pipeline introduces a certain amount of overhead, such as the time it takes to move an instruction from one stage to the next. If the number of stages is increased, this overhead can also increase, which can decrease the overall throughput.

3. Diminishing Returns: There's a point of diminishing returns with pipelining. As the number of stages increases, the time saved by having more stages decreases. This is because each additional stage provides less benefit than the previous one.

So, while pipelining can increase instruction execution throughput, simply increasing the number of pipeline stages doesn't always lead to a proportional increase in throughput. It's a balance that needs to be struck.