During which of the given years increase in number of hotels over the previous year was highest?

Increase in number of hotels over previous years = (number of hotels in previous year - number of hotels in current year).
Increase in number of hotels over previous years are as follows:
In 2004, 440 - 410 = 30
In 2005, 570 - 440 = 130
In 2006, 740 - 570 = 170
In 2008, 838 - 710 = 128
Hence, in 2006, increase in number of hotels over 2005 was highest.