Safaricom investors eyeing market share, ARPU

* What: Safaricom annual results

* When: Thursday, May 21

* Has competition eaten into market share?

By Helen Nyambura-Mwaura

NAIROBI, May 18 (Reuters) - Investors will be watching to see whether competitors have eaten into Safaricom's (SCOM.NR: Quote, Profile, Research) market share and revenue per user when east Africa's biggest mobile operator announces its full-year results on Thursday.

East Africa's biggest firm by market capitalisation said in March that its market share had dropped to about 77 percent from 84 percent at the end of March 2008 as a result of aggressive competition from rivals Orange, controlled by France Telecom (FTE.PA: Quote, Profile, Research), and Kuwaiti-listed Zain (ZAIN.KW: Quote, Profile, Research).

"The most critical thing is how the competition, with the entry of the new guys, has eaten into their market share," said Fred Mweni of Tsavo Securities.

"How resilient are they? How stable is their business and is it easily perforated by new players?"