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SAN FRANCISCO (Reuters) - The Dow Jones Industrial Average .DJI hit 20,000 for the first time ever on Wednesday in an ascent from 10,000 that has taken almost two decades.

It took just 42 sessions for the Dow to climb between 19,000 and 20,000, the second-fastest rise between 1,000-point milestones in the average’s 120-year history.

The Dow’s surge in recent months has been fueled by expectations that U.S. President Donald Trump will deregulate banks and stimulate the economy. Hitting 20,000 is seen by some as a psychological milestone that underscores Wall Street’s recent optimism.

But longer-term, the Dow’s performance appears less impressive. Its ascent from 10,000 to 20,000, doubling in value, has been sluggish compared to the time it took for the Dow to double in value three times in the late 1980s and 1990s.

If the Dow closes above 20,000 on Wednesday, it will have taken nearly 18 years for the average to double after it closed at 10,000 in early 1999 at the height of the dot-com boom.