It heavily depends on both other lenders and the bitcoin price vs. USD.
Rising prices usually mean traders need more money for long positions, so lots of loans get taken. Also if there are a lot of other lenders it might push down interest.
As you would directly compete with me by lending out money, why should I help you?
I made good returns so far, what also has to be considered is that you can either lend out 10 hours at 100% or 1 hour at 1000% so idle funds are not that bad if there are traders who desperately need money once in a while. Its a bit of a poker game though...
Oh, and depending on other lenders and their "smartness" (auto lend at 2 digit rates per year if bitcoins grows at 2 digit rates per day...) it might not give as high returns as you might expect during rallies.
My average rate in bitcoins as of yersterday is nearly 2.7% apr over 55 days. For the 41 days of USD it is definitely higher.
If you were just buying 41 days ago and holding however, there might have been better returns still. Hindsight is always 20/20 though, so I chose the path with less risk. Still traders can make much more than lenders per day if I just look at the charts.
You could start small and check out the returns for yourself as they also depend on your lending strategy, also 1 reason why I built into this sheet the ability to track several deposits and not just an initial amount.