I have two questions:

1. **Why does the effective throughput (as defined below) decreases when the block interval is decreased?**
2. **How does a reduction in the block size results in maintaining a high effective throughput?**

The origin of these questions is as follows.
First, [this](https://fc16.ifca.ai/bitcoin/papers/CDE+16.pdf) paper about Scaling Decentralized Blockchains says:

> 
> To improve the system’s latency, we can in principle simply
>  reduce the block interval. To do so while retaining high effective throughput,
>  however, would also require a reduction in the block size. 
> 
> 
> 

which implies that the effective throughput decreases when the block interval is decreased. This results in my first question.

Second, they define *effective throughput* as follows:

```
X% effective throughput := (block size)/(X% block propagation delay)

```

This formula indicates a decrease in effective throughput when the block size is decreased, while their goal is the opposite, i.e. maintaining a high effective throughput (by decreasing the block size). This is what my second question is about.