Flat glass prices dipped slightly in January, decreasing 0.1 percent after a big jump of 1.8 percent in December, according to the latest Producer Price Index Report (PPI) issued by the U.S. Labor Department.

The PPI program measures the average change over time in the selling prices received by domestic producers for their output, according to the U.S. Bureau of Labor Statistics (BLS). The prices included in the PPI are from the first commercial transaction for many products and some services.

The flat glass index sits at 123.1, and prices are up 3.4 percent from January 2014.

In another report, import prices for glass and glassware dropped 0.1percent for the second straight month after a 0.2-percent dip in November. Import prices are down 0.8 percent from a year ago.

Meanwhile, export prices for glass and glassware increased 0.8 percent in January after rising 0.4 percent in December and 0.1 percent the month before. Export prices for glass and glassware are up 2 percent from this time last year.

Prices of materials for construction saw a slight increase of 0.1 percent in January following a minor dip of the same amount in December. Prices in that category are up 2.3 percent from January 2014. Final demand for construction rose 0.4 percent after sitting stagnant the two months prior. Those prices are up 1.9 percent from a year ago.

On the whole, the PPI for final demand fell 0.8 percent in January, seasonally adjusted, after a 0.3-percent dip in December and a 0.2-percent decrease in November. On an unadjusted basis, the index for final demand was unchanged for the 12 months ended in January.

Overall prices for U.S. imports decreased 2.8 percent in January following a 1.9-percent decline in December and a 1.8-percent drop the month before. Export prices declined 2 percent in January and haven’t increased since July.