Around the year 1850 about 500 pilgrims left the [then] Dutch East Indies for Mecca, on a total population of around 30 million Muslims. Over the course of the 19th century this would grow to around 15000, while in the first half of the 20th century it would continue to grow to around to around 30-50 thousand (on a population of 60 million).
The rise in people making the pilgrimage can be attributed to a number of causes. First of all; before the introduction of steamers the trip to Mecca could take many months, even upwards of a year. Few were in a position to make such a journey, as not only is it very expensive, it is also takes a physical toll on one's health. Only with the introduction of steamers became the pilgrimage more accessable, as the journey was reduced to 2-3 weeks. This brought the total time for the pilgrimage down to 3-4 months, rather than years. The modern steamers could also provide more comfort and better living conditions, making the journey take less of a toll on the body.
A second reason is a gradual liberalisation of governmental policies. In the early 19th century the Dutch colonial authorities had fought a war against the Padris on Sumatra. The Padris were wahhabi preachers radicalised while on pilgrimage to Mecca. The experience of this war, and other incidents involving religious ferver from Hajjis, led the colonial government to try and regulate the flow of pilgrims. A steep tax was imposed, anti-pilgrimage propaganda was spread and certain qualifications and limitations were imposed on prospective pilgrims. While they certainly had a limiting effect on the number of pilgrims (after the abolition of the tax the number of pilgrims grew 10 fold in a 5 years), in the end these measures proved in effective and were slowly abolished. And with it the number of hajjis grew rapidly.
Sources (all in Dutch):
http://www.npogeschiedenis.nl/nieuws/2012/oktober/Het-groote-Mekka-feest.html