BTC Tx Fee Index

This index tracks the the median BTC/kB per block.

Derivation Process:

1. Retrieve the median Sat/vB per block via the getBlockStats endpoint of Bitcoin Core.

2. The index contract stores the data cumulatively.

3. It's updated on a daily basis.

Example:

Block Number	Median Btc/kb per block	IndexBalance
0	20	20
1	13	33
2	5	38