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Holdings weighted values are in general more interesting than straight
counts, as the holdings weight is a better indicator of how likely a field
is to be relevant to actual searches.

If an element is used in 300 records, but has 300,000,000 holdings, it
seems to indicate a rarely assigned element that is nevertheless applicable
to some  widely held items.

If an element is used in 300 records, and has 300 holdings, it suggests a
rarely assigned element that either is  used in a few records that describe
unique items, or in is misapplied in  records which are not subsequently
re-used.

There does seems to be a slight bug in the way that these values are being
computed:
For example in http://experimental.worldcat.org/marcusage/650.html ,

TOTAL Occurrences:            113,003,641
Subfield a occurrences:       279,078,783 (2.5 : 1)
Overall number of Holdings: 1,501,877,652
Subfield a holdings:        5,840,127,920 (3.9:1)

It seems that the total/overall counts are in terms of records, but the
subfield counts are in terms of fields occurrences (if a record has two 650
fields with a $a, the subfield count will be increased by two, and
presumably the holdings count by twice the number of holdings) .

This does give some interesting information, in that it suggests that more
common holdings have more subject headings assigned, but it doesn't let us
compute what %age of records or holdings  that have at least one 650 use
subfield $a .

Field 245 shows some other curiosities:
http://experimental.worldcat.org/marcusage/245.html

Subfield 245 $k has 469,891 occurrences, but only 427,311 holdings;  this
suggests that there are records included in the counts which have zero
holdings.  These might be worth filtering out.

Simon

On Thu, Mar 7, 2013 at 10:11 PM, Tennant,Roy <[log in to unmask]> wrote:

>  It is the number of holding symbols attached to records that have that
> particular MARC element. For example:
>
> Record 1 with the subfield: 10 holdings
> Record 2 without the subfield: 30 holdings
> Record 3 with the subfield: 50 holdings
>
> Occurrences: 3
> Holdings: 60
>
> Roy
>
>
>
> On 3/7/13 3/7/13  6:47 PM, "Karen Coyle" <[log in to unmask]> wrote:
>
>    Roy, can you explain what the "number of holdings" figure represents?
> Is this a multiplier of the holdings on the records that have that
> field/subfield? (Sorry, I'm just having trouble wrapping my head around the
> variance in those numbers.)
>
>  kc
>
>
>
> On 3/7/13 4:33 PM, Tennant,Roy wrote:
>
>
>
> MARC Usage: Additional report available Maria Oldal of The Morgan had
> requested to see $a and $2 combinations for the 655 field, so I was able to
> generate that and place a link on the page for that field:
> <http://experimental.worldcat.org/marcusage/655.html><http://experimental.worldcat.org/marcusage/655.html>.
> Although I will be somewhat limited as to the number of ad hoc reports like
> this I can generate, go ahead and request anything you want to see and I
> will see if I can get to it. Thanks,
>  Roy
>
>
>
>