What is the highest number of people occupying the ISS at on time ?
1901 ISS was founded in Copenhagen , Denmark as a small security company with 20 night watchmen named Kjøbenhavn - Frederiksberg Nattevagt ( Copenhagen - Frederiksberg Night Watch ) 1934 ISS entered the cleaning business with the establishment of Det Danske Rengørings Selskab A / S ( The Danish Cleaning Company ) as an independent subsidiary of the security company1946 The first geographical expansion outside Denmark : Swedish subsidiary established1968 The company adopted the ISS name1973 Overseas expansion started1975 Group revenue reached DKK 1 billion1977 ISS shares listed on the Copenhagen Stock Exchange1989 The total number of employees in the Group reached 100 , 0001997 Strategy “ aim2002 “ was launched .