This has changed in the last couple of years, however. In mid-2004 most of the top ink suppliers started to work under the International Standards Organization's requirements for testing monochrome inkjet cartridges.

The ISO is recognized for developing standards for many different industries to offer a standardized, unbiased way of comparing or rating products.

With the ISO standards for printer cartridges, it give the consumer a reliable way of comparing brands and manufacturers of ink. The reported yield from their cartridges are all determined using the same methods, so the numbers are directly comparable.

The following are the things that are specified in the ISO standard:

- The test prints must use the printer's default settings

- The tests are performed under strict temperature controls

- Both the cartridges and the printers used for testing must be available to the average consumer

- 9 of each cartridge must be tested for statistical validity

- 3 cartridges must be tested on 3 different printers to eliminate a single printer causing the numbers to be skewed

Aside from raw numbers, you should also consider some other things when deciding on your ink supplier. These things include delivery, reliability, and general quality. It won't matter if a supplier has the best price if they can't get your cartridge to you on time or it's hit or miss whether it will work properly.

If you do a fair bit of printing, you can also keep your own notes about different suppliers to see which ones last the longest and are the most cost efficient. It never hurts to have more than one supplier you can deal with, in case they are ever out of stock of your particular cartridge model.