The Mecca Royal Hotel Clock Tower overshadows the Holy Mosque. (Fayez Nureldine -- AFP/Getty Images)

This week concludes the Hajj, the annual rite of pilgrimage to the Saudi Arabian holy city of Mecca, where the Prophet Mohammed first spread the faith that has since become known as Islam. The Hajj represents, among many other things, Saudi Arabia's unique place of prominence in the vast Islamic world, as well as an economic opportunity for the oil-dependent Saudi economy. Religious tourism, to which the Hajj is central, is a key component of the country's long-term economic strategy. The kingdom is planning for the day that the natural resource that's made it so rich dies out.

But religious tourism is also a touchy, even existential, subject for Saudi Arabia. The country has indeed succeeded in boosting tourism significantly, both in terms of revenue and arrivals, particularly since the 1960s and '70s, when poor infrastructure made travel within the country difficult. Yet religious tourism appears to be flat, judging by the number of arrivals who come specifically for the Hajj. In 1995, for example, the Hajj accounted for well over one in four foreign tourists. In 2009, the most recent year for which data is available, it was close to one in seven. Here's the available data for all foreign visits and foreign Hajj visits. As you can see, the blue line (all tourists, data from the World Bank) is trending way up while the red line (Hajj arrivals, data from the Saudi government) looks flat:

(Data: World Bank, Saudi government)

The economics of this are straightforward. The Hajj is just a few days, and Mecca and other Hajj sites are only so big, which means that Saudi tourist facilities hit capacity pretty quickly. The government could upgrade its facilities to allow for more Hajj tourists, but that would be really expensive. The new tourists it would allow would be less wealthy than the current Hajj arrivals, and the new facilities would sit empty for most of the rest of the year.

Prominent Saudi journalist Abdul Rahman al-Rashed does the math and finds the economic case for expanding Hajj tourism is weak, even though the Muslim world's rising middle classes are showing increased willingness and interest in the annual pilgrimage:

[The Saudi government] has taken numerous steps to accommodate three million pilgrims in the holy city; to ensure their transportation to and from the holy sites and also to make sure that they perform Haj rituals easily and comfortably. There are no more steps left to be taken for Haj and not more than 3 million pilgrims will be able to perform this holy duty. Even if the capabilities were doubled it is impossible that their number will exceed four million.

But this suggests an existential dilemma for the country, whose identity is wrapped up in both its religious legacy and its holy duty to serve the Islamic world. The kingdom's monarch bears the official title Custodian of the Two Holy Mosques and the nation's influence in the Islamic world comes largely from its legacy as Islam's birthplace. Saudi blogger Ahmed al-Omran points out that the kingdom could in fact do much to make its holy sites more accessible to the world's Muslims, but has instead focused on developing non-religious tourism.

"They are turning the holy sanctuary into a machine, a city which has no identity, no heritage, no culture and no natural environment," Sami Angawi, founder of the Hajj Research Centre, told the Guardian recently (quote via al-Omran). The short-term economics of Saudi tourism would seem to support doing exactly that. But, as Angawi hints, there are bigger and more existential issues at stake for Saudi Arabia than just tourism revenue.