I am. Since IB lends out a proportion of how many shares are eligible to be shorted, I can calculate real-time availability by percent. Since 10% of my shares are being lent out, it means 90% of all eligible shares have not been lent out.
For example if 1 million shareholders (with 1 share each) allowed their shares to be shorted, only 100,000 shares have been shorted indicating that there is "high" availability of shares to short.
IB receives ~1.4% of the collateral value, and they give me half at 0.7%. As the stock becomes harder to borrow, the rate they collect and the rate I collect increases. It is an annualized rate but interest is calculated daily.
So you get an annualized .7% of 10% of the value of your Tesla stock? So currently, an annual interest of .07%?