Suppose there is no official minimum wage and the lowest-paid workers receive $16.00/hr. If the government then enacts a minimum wage of $10.00/hr, will it have any effect?

There will be an effect as there might be labor shortage.

Explanation: Minimum wage is the least renumeration pay that can legally be paid by employers to their workers. It is a price floor method below which employees can't sell their labor. When a minimum wage is imposed by the government, firms are not allowed to pay less than the wage rate mandated by the government.

If the minimum wage is set below the equilibrium wage rate, quantity of labor reduces in comparison to the quantity demanded by employers. If the least paid person is paid $16 per hour and the government imposes a minimum wage of $10, There will be a shortage of labor because most people won't like to work as a result of the lower income. It also leads to lack of motivation among workers.