Turkey's calendar-adjusted industrial production dropped 6.5 percent in November 2018 compared to the same month the previous year, the Turkish Statistical Institute (TurkStat) announced Monday.

Industrial output is considered a vital indicator for the economy, as it is seen as a preliminary gauge of GDP growth.

Among three main sub-indexes, the manufacturing index posted the worst performance in November, down 7.1 percent year-on-year.

The electricity, gas, steam, and air conditioning supply index fell 1.8 percent, while the mining and quarrying index went down 1.1 percent during the same period.

The term "calendar-adjusted" is used to refer to data without calendar and holiday-originating effects.

According to a survey conducted by Anadolu Agency's Finance Desk on Friday, a group of 11 economists projected the calendar-adjusted industrial production index to fall 3.1 percent year-on-year.

On a monthly basis, industrial production dropped slightly, 0.3 percent in November, TurkStat data showed.

Among the sub-sectors of the seasonally and calendar-adjusted industrial sector, the mining and quarrying index fell the most monthly.

The mining and quarrying index dropped 3.7 percent in November, compared to October 2018.

The manufacturing index dropped a slight 0.1 percent month-on-month in November, while the electricity, gas, steam, and air conditioning supply index remained unchanged.