The latest statistics for initial WCA's show that the total time taken in June 2019 was still at an average of 19 weeks.
These figures are for initial ESA claims, reassessments usually take longer.

See the chart on page 11, note that the numbers for each stage don't seem to add up to the total.
In particular the time it's taking after assessment for the DWP to make a decision is wrong in that chart.

The graph on page 12 shows it better, it's taking around 10 weeks from the claim to having an assessment and the result sent to the DWP, it is then taking another 9 weeks for the DWP to finalise the decision.

People often ask about regional figures so I have managed to use Stat-Xplore to get a regional breakdown for the June 2019 figures which are the latest published.
Again remember that these times are for WCAs for new ESA claims, reassessments usually take longer. (New WCAs in UC are also not included).

15 weeks North East
13 weeks North West
14 weeks Yorkshire and The Humber
18 weeks East Midlands
18 weeks West Midlands
17 weeks East of England
18 weeks London
17 weeks South East
20 weeks South West
18 weeks Scotland
18 weeks Wales