You can because it is easiest, but the easy way is not the responsible way. Here is how it could work:

1. GameStop, Target, Wal-Mart, Best Buy and other brick and mortar retailers keep track of individual video games sold via receipts in their database at the point of sale. 

2. Amazon, Ebay and other online retailers keep track of individual video games sold via online receipts.

3. NPD, VGChartz and others base their numbers entirely off of retailer sales numbers. Internal numbers from Sony, Nintendo, Microsoft and the publishers are used as a reference to gauge the difference between sold vs. shipped.

4. Publish the sold numbers with the shipped numbers side-by-side.

By receipts I mean exactly that little strip of white paper the consumer receives and is logged into the company's database at the point of purchase. Should not be too hard to get ahold of, but Wal-Mart and the brick and mortars would most likely want money for that information .

I am also assuming the sale of used games in the equation. I have received a receipt for a used game.

 That will still give you only a sample size for areas that you have data for not everywhere. unless you have tracking data from 64 countries world wide as an example of the number of countries the PS3 was shipped to world wide when it was first released in 2006 as an example and than you have to break that down by cities in each country..than it's very unlikely you will ever get a true world wide tracking data because the only one's who once again have that is the restock reorder request that Sony, nintendo or Microsoft get's from shipping regions.

you can make a projected guess based on the retail selection's you have in certain cities or countries..but it is still a projection of a sample size that is a guess of that data.

you can lump everyone into a region but it does not mean you have data from all those region's that you have lumped together in there.

It's blind faith to believe that Sony is going to go from 2.7 million consoles produced in one year to 27 million the next year, year that it's the last in that console's lifespan. Apply Occam's razor here, what is the most plausible explanation? That this guy made a mistake reading the reports, or that every tracking service is so wrong to hide an enormous amount of PS1s?

PS: with all my respect to the emerging market's people, do you really think Sony is going to sell a similar number of consoles there, in 3-4 years, than in ten years in Europe?

or the fact that no one cared to even check the data until This recent interview on the playstation 1's total sold number's data!

the point being it's very unlikely every tracking service does not have tracking data capability to every region country or city that these systems are sold to unless they are the companies themselves. and that is information that none of them are going to share..other than that their just guessing. not to say it's not a good guide line for their guesses, but they are not going to be accurate 100% world wide. esp. since Sony has been putting the playstation platform into more countries world wide than the other two.

think about that for a sec,how many countries  are we talking about here..that is the point those emerging market's may not be prime for something like the PS3 in sales for 2006 but say something like the PS1 could do very well there it's cheaper to produce and it get's their platform into hands that may have never had a playstation before.

just look at right now the PS2 just went to some countries for the very first time in it's 9th and now 10 year.

It's not the number of countries, or the population, that you have to compare. You have to compare the economy and videogame tradition on those markets, with the same parameters in Europe. Togo, Kiribati and West Samoa don't buy the same number of PS1s than UK, France and Germany. This is becoming sheer idiocy.

So too are the GC, Xbox, Dreamcast, PS3, X360 and Wii, GBA, DS and PSP.

Stop talking about things that are beyond you.

what...?

"You have to compare the economy and videogame tradition on those markets, with the same parameters in Europe"

why..because it's europe?

how noble of you

that's like saying IF my company ship's more product in more part's of the world than you ship your products there but your saying that you can only use parameter's of europe.

one countrie counts just as much as another

or is that because you have tracking data there back in 2006 only for EUROPE but you do not have any in that area but you just guess for that regionnever mind that maybe just maybe there is more sales of a product that you do not have tracking data for?

that's the problem how can you claim world wide tracking data when you cannot get world wide tracking data..

it's very simple you guess.

nothing wrong with a guess people guess all the time..hey you can get within 10% of the sales data tracking in some parts of the areas you have data coming in from. good job that makes a great guide line..but hardly 100% accurate

great love the snide remarks..keep going prick.

What I'm saying is that 3rd world countries won't buy in 3-4 years the same amount of consoles than Europe, or Japan, in 10 years. It's simple to understand. It doesn't have anything to do with being noble, or a bastard, it has to do with economy. When you need every coin you earn to buy food or to have somewhere to sleep, you don't buy videogames.