September 2019 is the 31st month that the Nintendo Switch has been available for. During the latest month the Switch caught up with the Wii by 740,022 units. In the last 12 months the Wii has outsold the Switch by 4.21 million units. The Wii is currently ahead of the Switch by 10.76 million units.
The Wii launched in November 2006, while the Nintendo Switch launched in March 2017. The Switch has sold 38.75 million units, while the Wii sold 49.51 million units during the same timeframe.
The 31st month for the Nintendo Switch is September 2019 and for the Wii it is May 200
source: gamezpot.com