Actually, I have to correct myself, the mathematical absolute minimum the PS2 sold is 159.2mil. and the mathematical absolute maximum is 161.9mil, taken from Resetera: https://www.resetera.com/threads/what-was-the-lifetime-sales-of-the-ps2-not-158m-update-between-159-2m-and-161-9m.77277/

Two snippets out of the discussion from ZhugeEX (Senior Analyst at Niko Partners):

1.
It's fairly simple.

PS2 Production Shipments were 117.9 million as of March 2007.
At this point Sony switched from reporting production shipments to hardware sell in.
Hardware sell in at this point was 115.6 million. So you can see there is a slight difference between Production Shipments vs Hardware sell in due to difference in reporting methods.

PS2 sold a further 39.5 million units through to March 2012 which takes the sell in total to 155.1 million.

In the fiscal year ending March 2013 a total of 16.5 million PS3&PS2 units were shipped. PS2 was still being shipped during this period so the info we're missing is how many units were PS2 and how many were PS3. Using PS3's 80m sell in announcements as a guide you can work backwards and ultimately work out that PS2 must have been close to 4m.

So whilst we don't know the 'official' number. We do know it was 155.1m as of March 2012 and there was another few million shipped shipped during the 9 months after that.

2.
The minimum would be 4.1m in FY12 and the maximum would be 6.8m.

PS2 is likely up YoY in FY12 as it is not mentioned as being down, like it is in prior reports. So with that in mind, and to align with PS3 hitting 80m in November we can say PS2 LTD is a minimum of 159.2m and a maximum of 161.9m. Most likely being closer to the former number.

I think the number must be closer to 159.2mil because 1. the PS2 was on it's very last leg in FY2013, so it's only logical that the shipping numbers must have been at the lower end and 2. if the PS2 would have sold 160mil, certainly, Sony would have reported it as it makes sense to report such a milestone, like it has announced the 150mil mark.

For me personally, if the Switch reaches 160mil, it will have definitely sold out the PS2 unless Sony or some credible source (like Shawn Layden came up with the exact lifetime sales of the PSP) come up with a definitive number. However, I hope the Switch will reach 162mil as at that point it's mathematically proven that it sold out the PS2. I hope that not as a Nintendo-Fanboy but because it would put an end to all theoretical discussions.

very interesting.

From October data and half of November for Japan i think Q3 will be something like this

Japan: 2.09 > 1.57 (-25%)
Americas: 3.07 > 2.45 (-20%)
Europe: 2.42 > 1.94 (-20%)
Other: 0.65 > 0.71 (+10%)
Total: 8.22 > 6.67 (-19%)

Year over year Other was 250k up in Q1 and 110K up in Q2 so i expect it to be slightly up in Q3.

I can't see how people think the PS2 is at 161 million, i think 158 to 159 million is almost certain and this is because of the PS3 numbers that were combined with PS2.

FY Mar 2012: PS2 total - 155.0m, PS3 total - 63.9m
FY Mar 2013: PS2 + PS3 - 16.5m for the FY, PS2 production ended
FY Mar 2014: PS3 - 7.0 million
FY Mar 2015 : PS3 - 3.1 million
FY Mar 2016: PS3 - ???, PS3 production ends in Europe
FY Mar 2017; PS3 - ???, PS3 production ended in October for NA and March in Japan.

So PS3 is at 74.0 million from known yearly shipments which means it needs 13.4million from 3 FY's missing and FY16 and FY17 were very low due to production ending and the PS3 not even being mentioned in Sony's yearly reports. If PS2 shipped 161 million then that means PS3 only shipped 10.5 million in FY13 and 2.9 million for FY16 & 17 combined. Shipments of 2.9 million for PS3's final two FY's is far too high. I think PS3 shipped 12.8 million in FY13, 500k in FY 16 and 100k in FY17 for it's known total of 87.4 million, this means 3.7 million for PS2's final year and 158.7 million total.

I think the crucial calculation part is from ZhugeEX:

In the fiscal year ending March 2013 a total of 16.5 million PS3&PS2 units were shipped. PS2 was still being shipped during this period so the info we're missing is how many units were PS2 and how many were PS3. Using PS3's 80m sell in announcements as a guide you can work backwards and ultimately work out that PS2 must have been close to 4m.

It's those 80mil PS3's shipped by November 2, 2013 (link of announcement: https://web.archive.org/web/20140210005326/http://scei.co.jp/corporate/release/131106_e.html) were you can start the calculation backwards as Sony stopped shipping PS2 from April 1, 2013 onwards. I'm not good at math but ZhugeEX and others on Resetera did the calculation and came to the conclusion that the range must definitely be between 159.2 and 161.9mil. Personally, I think 159.2mil is spot on. You can have fun with numbers, taking the above 80mil PS3's and calculate with official numbers from Sony's historical data: https://www.sony.com/en/SonyInfo/IR/library/historical/

Anyway, I think right now we are still too early in Switch's lifecycle for starting to count peanuts.

Sony shipped PS2 till April of this year? Man, that's a hell of a long time for market life. 23 Years. Damn, PS2 should've reached 200M by now.

Here in Brazil the PS2 was a fever. I got mine in 2010, and it was still the most popular system around. Games like GTA San Andreas and Pro Evolution Soccer were some of the most famous titles

I'm not sure if the Xbox 360 dethroned it, but to be honest, I doubt it.

Wait what!?! PS2 has been shipping until April 1, 2023? 
Why does this unironically end on April Fools Day? lol

Ok, that is a long lifetime, have they been producing?
Sony said they stopped production and discontinued the PS2 as of January 4th, 2013.
How have they been shipping for the past 10 years?

When I was a kid, I also got a hacked ps2 as a gift from parents with 5 pirate games in the bundle. I remember how easy was to get new games, with people selling in the streets (famous "camelôs") for R$10 in a 3 games bundle.

Obviously this practice persist till today by people with a low incomes and the hackin technology evolved a lot to the point you can get a practically new ps2 with hundreds of game built in (including old Nintendo games) for US$100

X360 also got a similar treatment but no way in the same league as ps2

Relax. He obviously meant April 1, 2013. Just a typo.

And yes it was officially discountinued January, however it was shipped and officially included (or counted at least internally by Sony) in the fiscal report for the quarter ending on 31.03.2013, That's why he is saying April 1st. So yeah You can tell that shipments of PS2 officially ended in the first calendar quarter of 2013.