Network: BGP vs RIR IPv4 assignments

I have compared the values obtained from each registry against the prefixes announced in BGP (BGP potaroo IPv4 stats) and the results are presented on the chart. As far as the biggest registry is concerned (ARIN) the number of "active" prefixes (broadcasted in BGP) is significantly lower (at level of 60%) comparing to the number of assigned prefixes. Utlization rate of the other rirs is on a quite high level (for the smallest ones there are one or two prerfixes not announced in BGP). In the article I enclose the chart and the table presenting the values.

Registry	BGP announced	Allocated	Percentage
Afrinic	1	2	50%
Apnic	34	43	79%
Arin	59	97	60%
Arin	59	97	60%
Lacnic	5	7	71%
Ripencc	32	40	80%