Sentence:  Though the number of people flowing in and out of our metropolitan areas each day has increased tremendously since World War 2 , , total annual rail commutation dropped 124 <WSD>million</WSD> from 1947 to 1957 . 
Meaning of the word marked with <WSD> tags:  (in Roman numerals, M written with a macron over it) denoting a quantity consisting of 1,000,000 items or units