These are your property taxes.  The tax rate shown to the right is an average of the rates levied against your three zoning types (Residential, Commercial, Industrial).  If you wish to alter taxes on a specific zone, then click on the book to the right.
    The arrows to the right of the percent box will increase or decrease your tax rate by one.  The minimun tax is 0% and the maximum is 20%.  A tax rate of 7% is average.  Low taxes attract citizens and business.  High tax will drive them out, but earn you more.