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Over the past three years , businesses have been cutting back their travel expenses to save money , and now experts say they 're going to keep doing that , even when the economy picks up , e-mail , video , web conferencing becoming popular alternatives to face - to - face meetings , also finding cheap fares on Internet or using low fare airlines .
 the past three years
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: date, organization, person, geographical social political, national religious political, facility, cardinal, location, work of art, law, event, product, ordinal, percent, time, quantity, money, language 
Text: {0} 
Answer:
 the past three years