28 PEOPLES OF THE PHILIPPINES 
barely to semi-civilization. If we accept the population 
of the archipelago at the time of discovery as approxi- 
mately two-thirds of a million, it contained then about 
as many souls as lived in what is now the United States 
in an area twenty-five or thirty times as great. Even 
at the lowest computation, five inhabitants per square 
mile must be allowed the Philippines in the _ pre- 
European period. This is a higher figure than prevailed 
in any regions of the aboriginal New World other than 
certain parts of Mexico and Peru. 
An acre of rice grown under irrigation or in swampy 
land supports from three to five persons, or very nearly 
an average household, in Java, in the Christianized 
portions of the Philippines, and among the primitive 
mountaineers of Luzon. As the labor required to farm 
such a tract is in most cases rather moderate and leaves 
certain seasons of the year entirely free, it is clear both 
how a considerable condensation of population could 
have taken place in prehistoric times, and why the 
population has tended to increase steadily at a consider- 
able rate ever since. In 1591 Spanish tribute lists 
indicated a population, at the estimated ratio of four 
souls to one tribute, of 667,000. This figure excludes all 
the unsubjected mountain tribes and all the Moham- 
medans; in fact, almost the whole of the island of 
Mindanao. For two centuries increase continued, 
though rather slowly. In 1800 there were about a 
million and a half Christians in the archipelago. By 
1840 this number had doubled, and by 1887 had doubled 
again, to six millions. The American census of 1903 
showed nearly seven million Christians, and the latest 
estimate, for 1916, reckons 8,400,000; to whom more 
than a million Pagans, Mohammedans, and foreigners 
must be added. The present rate of increase is at least 
one and one-half percent annually, and unless adversely 
