Zero Bound

I have had a TreasuryDirect account for many years.  This is linked to a bank account and allows you to buy and hold government securities.  From time to time I have used it to buy Treasury bills (TBills) which are government bonds which mature in a year or less.  Bills are sold at a discount and redeemed at their face value when they come due.  You can arrange to have the bills rollover when they come due.  That is the redemption amount is used to buy a new bill (of the same term and amount) with the discount remitted to your linked bank account.  

I had been rolling over 13 and 26 week bills for some time but eventually stopped and moved the money back to my bank account after interest rates remained near zero for years after the financial crisis of 2008.  When interest rates recovered a bit (to around 2%) in 2019 I started buying and rolling over bills again, this time 4 and 8 week (which I don't think they used to offer).  But the COVID epidemic has again caused rates to fall to near zero.  And in the case of the 4-week bills not just near zero, actually zero.  The last few auctions have settled with a zero interest rate.  This is a little annoying although it does have the advantage that I don't have to deal with recording the tiny deposits from a near zero rate.  But it will be really annoying if the rates go negative which they theoretically could do.  I expect the government will try to avoid this but if they don't I will stop the rollovers.  Perhaps I should anyway, my bank isn't paying a lot of interest but it is more than zero.