You know, if you hold Steem Dollars, either in liquid form or savings, you'll earn interest. Compound interest is explained in this wikipedia article.
[Image source, by Jelson25 - Own work, CC BY-SA 3.0]
However, the interest will only be paid when the balance of your account changes. The algorithm is:
- there is a
last interest paid timefield stored in your account - every time after balance changed, if last interest paid time is not less than 30 days in the past, interest will be calculated and paid
- a simplified formula is:
interest = average_balance_since_last_interest_pay * daily_interest_rate * days - daily interest rate is calculated as
annual_rate / 365. For example, current annual interest rate is 10%, daily rate is calculated as10% / 365 = 0.0274%.
If you have 1000 Steem Dollars, and
- if you move funds once a month, the interest paid to you will be around
1000 * (1 + 10% / 12)^12 - 1000 = 104.7 SBD(calculation link) - if you move funds once a year, the interest paid to you will be
1000 * 10% = 100 SBD
Which means, if you don't move funds in time, you'll loss the compound interest.
How about someone make a bot to collect compound interest for its subscribers? The bot only need to send 0.001 SBD to subscriber's accounts once every month. Perhaps with a subscription fee of 0.002 SBD per account per month?
--- end of English part ---
你知道，如果你持有 Steem Dollar ，不管是在流动账户还是储蓄账户，你会挣到利息。复利介绍参见这篇英文文章）（如果链接打不开，请自己百度）。
[图 来源， 作者 Jelson25 - 自创， CC BY-SA 3.0]
但是，利息只会在你的账户余额发生变化时才会支付。算法是：
- 账户里存储了一个“上次利息支付时间”
- 每次当余额发生变化时，如果上次利息支付时间在30天以前，则会计算并支付利息
- 简化公式是：
利息 = 上次支付利息后平均每天账户余额 * 天利率 * 天数 - 天利率计算公式是
年利率 / 365。比如现在年利率是 10% ，天利率计算公式是10% / 365 = 0.0274。
比如你账户里有 1000 Steem Dollar，并且
- 如果你每月动一次账户，则一年总利息大约是
1000 * (1 + 10% / 12)^12 - 1000 = 104.7 SBD(计算链接) - 如果你每年动一次账户，则一年总利息是
1000 * 10% = 100 SBD
这意味着如果你没有及时动一下账户，你将不会获得复利。
如果有个机器人，专门为客户收集利息，会怎么样？这个机器人只需要每个月给客户转账 0.001 SBD 即可。可能机器人可以设置个每月每账户 0.002 SBD 的服务费。