Hereafter minimum annual salaries and compensation shall be paid to police officers and policemen, in incorporated cities of this state, in accordance with the following schedule: in incorporated cities having more than 500,000 population, police officers and policemen with more than 3 years police service shall receive an amount not less than $2,640.00 per year; in incorporated cities having a population of more than 75,000 but not exceeding 500,000, police officers and policemen with more than 3 years police service shall receive not less than $2,000.00 per year; in incorporated cities having a population of more than 25,000 but not exceeding 75,000, police officers and policemen with more than 2 years police service shall receive not less than $1,900.00 per year; in incorporated cities having a population of more than 12,500 but not exceeding 25,000, police officers and policemen with more than 2 years police service shall receive not less than $1,800.00 per year; in incorporated cities having a population of more than 5,000 but not exceeding 12,500, police officers and policemen with more than 1 year police service shall receive not less than $1,700.00 per year.