Could NPD be Wrong?

[Viper1]

NJ5 said:

It's actually pretty easy to prove that NPD's public data isn't completely trustworthy.

They never publish corrections to their past data. This means that either:

1- Their data is always correct the first time (quite unlikely given they don't receive sales data from Walmart and other big retailers)
2- They simply forget about past errors and carry on (adding up several months will result in wrong data, as well as each month's data being sometimes wrong).
3- They adjust for past errors by adjusting later months' data. In this case it's not possible to trust each month's data, since it may be wrong or adjusted up or down to account for past mistakes. At least in this case the sum of several months should be more close to the truth.

Take your pick, since we don't really know what they do. There's no transparency at all with NPD's numbers.

 

That is what they do.  This has been confirmed by some of their own clients.