I have seen a few articles lately which discuss the interest rate paid on HBD in Savings. These articles have many comments, indicating that people are interested in this!
Right now, HBD which an account holder has moved to the Savings part of their HBD Wallet is earning 12% per year, paid monthly. This means you will receive ONE HBD for every 100 in your Savings, every month. Nice! But is 15% or even 20% nicer? We all would like to get the best possible return on our money but what are the consequences for the entire Hive blockchain? That is a matter for debate!
HBD interest comes out of thin air! It is automatically created by the blockchain in order to pay the interest at the current rate that the witnesses decide is best for Hive by signalling their desired rate. You can see what every witness is signalling on the Peakd Witnesses page.
HBD is a debt of Hive. It is Hive that is converted to HBD and can potentially be converted back to Hive by the conversion process that takes 3.5 days.
ONE HBD can always be converted to ONE US Dollar's worth of HIVE, at a rate determined by the average price of Hive over the previous 3.5 days.
Today I commented on this post (@themarkymark/signalling-for-20-hbd-interest by 
the word "MEDIAN" which is clearly indicated on the Witness page as the mathematical method used to calculate the HBD interest rate.
For those who want a definition of MEDIAN, you can go to https://byjus.com/maths/mean-median-mode/ and see
median represents the mid-value of the given set of data when arranged in a particular order
So if we have this list: 1 3 4 7 7 8 9
the Median value is the middle value, which is the first 7, so the Median is 7.
I assume this is how the HIVE code calculates the interest rate - by ordering the witness's signaled interest rates from low to high and then picking the middle value.
I made this spreadsheet which calculates the MEDIAN value of the current HBD interest rates shown on the Witness page for each of the top 21 witnesses:
I think you should be able to view the spreadsheet and maybe download it so you can play with it yourself. Here is a screenshot of it:
As you can see, the spreadsheet shows the current HBD interest rate as 12% which it is!
The formula to calculate the median is super simple!
=MEDIAN(B2:B22)
I just copied the current spreadsheet and pasted it to the right, with the "HBD INTEREST" column renamed "HBD INTEREST EDITS". Now we can change some Witness interest values and see what happens to the calculated HBD Interest Rate (Median).
What happens if ALL witnesses who were under 12 changed their rate to 12? Nothing! The Median is still 12. In this experiment, 11 witnesses are at 12, and 12 is the lowest number, so the median (the 11th number when ordered from lowest to highest) is 12.
NEXT, what happens if ONE of these hypothetical witnesses now voting for 12 changes their vote to 13? Well then that 13 is the 11th value in the low to high list, so it becomes the new interest rate! If that One witness changed their number to 14 or 15, then the new interest rate would be 14 or 15. if they changed it to 16 or more, then the new interest rate would be 15.
Or maybe an app or website that updates the witness HBD interest rates in real time? Might be good to have. Maybe I'll make a website page where we can all see this Median calculation in real time based on the latest Witness numbers.
Please let me know if you find any errors in my thinking or methodology. I'll come back and edit this post if needed. Thanks everyone!
