They do base this on the number of publications that are ordered, magazines, books, and "special order" items. I can imagine that people are ordering cds, dvds, insight volumes, etc, and not donating much. Too many jws are only concerned what humans see, not God.
As if they ever donated enough:
*** km 11/96 p. 3 Share With Others According to Their Needs ***
Jehovah makes provision to fill our spiritual needs through the faithful "slave." (Matt. 24:45-47) Many of these provisions are in the form of books, Bibles, bound volumes, videos, audiocassette recordings, and computer disks for Bible research. What Jehovah supplies is always sufficient without being wasteful. He expects us to share with one another, making sure that all benefit equally.
All such provisions are produced at tremendous financial cost. These expenses are cared for by the worldwide brotherhood. This is especially true since the organization instituted the arrangement to distribute literature without charge, depending entirely on voluntary donations to cover the expense. Additionally, many branches obtain these provisions from the Society at a cost that enables the brothers to have what they need for meetings and field activity even though they have very limited material resources.
HowWeCanHelp: We can respond to Paul’s admonition to share with others "according to their needs." (Rom. 12:13) When we make financial contributions toward the worldwide work, we are directly sharing what we have with our brothers around the world. With this in mind, some have decided to set aside an amount to contribute to the worldwide work each month, just as they do for Kingdom Hall expenses. They recognize that these funds are used not only for literature production but for all facets of the work as well. Imagine the great benefit our worldwide brotherhood would experience if more would share in this way on a regular basis.
Further, we can share with them by always being conservative when requesting items that are readily available to us. Ordering only what we actually need allows our brothers elsewhere to receive the spiritual provisions that they also need to keep strong and to advance the preaching of the good news in their part of the world.—Heb. 13:16.
We should especially bear this in mind when we request items that are produced at considerable expense to the Society. These include videos, CD-ROMs, large reference books, bound volumes, and audiocassette subscriptions. Rather than requesting one item for each member of the household, could the entire family get along with just one? If we limit what we take for ourselves, it will allow others to obtain the same good things that we enjoy.—Phil. 2:4.
The cost of literature that we place in the field may be offset in part by donations to the Society’s worldwide work offered by us at the Kingdom Hall and by interested ones who accept it. However, when it comes to literature items we request for our personal use, including songbooks, Yearbooks,
deluxe Bibles, and so forth, we cannot expect outsiders to care for our needs. Jehovah’s dedicated servants are the primary source of this financial support. With that in mind, many publishers estimate what these items might cost if commercially produced, and then they contribute accordingly. For example, a deluxe, gold-edged Bible can easily cost $20 or more, a reference book may be $40 and up, a full-color wall calendar may sell for at least $5, an encyclopedia on CD-ROM costs from $50 to $100 or higher, music compact discs commonly cost close to $20, and some videos are often sold for much more. A failure to contribute enough to cover costs will ultimately restrict what the organization may otherwise be able to accomplish in furthering the worldwide work.
Jesus declared that his true disciples would be clearly identified by their love for one another. (John 13:34, 35) Our generosity in giving materially and our unselfishness in sharing with others according to their needs are surely fine ways to prove ourselves to be genuine Christians.