The conronavirus-driven slump in U.S. equities has seen U.S. stocks wipe out 81% of their gains since President Trump took office.

The S&P 500 index fell 260.75 points, or 9.5%, to 2,480.63 on Thursday, following an Oval Office address from Trump Wednesday evening that did nothing to calm fears over the spread of  the coronavirus.

Thursday saw a growing list of forced limits on public gatherings, suspensions of sporting events, and even the closure of Broadway theaters in response to the coronavirus.

With Thursday's declines, the S&P 500 has lost 913 points since its all-time high of 3,393.52 set Feb. 19. That’s equivalent to 81% of the index’s gains between Trump’s inauguration on Jan. 20, 2017 and the peak.

The index has lost 72% of its gains for the period between Nov. 8, 2016, when Trump’s election victory first set a fire under equities, and the Feb. 19 peak.

Thursday's action pushed the S&P 500 well into so-called bear market territory, a 20% decline from recent highs. The Dow Jones Industrial Average fell into a bear market Wednesday. The moves have effectively marked  an end to the longest bull market in U.S. history which began almost exactly 11 years ago on March 9, 2009.

The S&P last closed below its current level on Jan. 2, 2019.

Of course, the heightened volatility of recent days means that the S&P 500 could claw back some of its losses fairly quickly, in the event the coronavirus economic impact is somehow contained. However, it would take nearly a 37% rise in the S&P 500 to reclaim the heights from which it so recently and spectacularly has fallen.

The gains for the S&P 500 during the 3 years and 2 months of the Trump presidency now stand at 9%.