U.S. swap spreads reached historical lows...

U.S. swap spreads in all tenors reached historical lows and it seems going on.
It's maybe due to supply and demand side rather than fundamental or structural changes.
Among below 3 interpretations, last one, of DB's seems most reasonable.

(1) JPM explains the burden of High Grade issuance swapped weighs on the spread. If then, this pressure would be going during this month.

(2) CITI estimates dealer position is tilting toward lower long-end swap rate as well. As sure, they see this as a temporary event, so they forecast it would be normalized at the end of this year.

(3) DB says swap spreads plumbed new lows last week as corporate issuance flows continued to weigh on the market in an environment of low liquidity, low balance sheet capacity, and in part due to stop outs of paid positions entered prematurely.