HOUSTON, Jan. 2 (Xinhua) -- The U.S. Energy Information Administration (EIA) published a report on Tuesday, showing that energy commodity prices increased in the second half of 2017.

According to the report, after decreasing nearly 20 percent in the first half of 2017, the spot energy index in the Standard and Poor's (S&P) Goldman Sachs Commodity Index (GSCI) ended 2017 16 percent higher than the beginning of the year.

Higher crude oil and petroleum product prices in the second half of 2017 were responsible for the increase in the S&P GSCI energy index, the report added.

West Texas Intermediate (WTI) and Brent, two major crude oil benchmarks, account for 70 percent of the weighting in the S&P GSCI energy index. As a result, the energy index tends to follow major price movements in the crude oil market.

The weights associated with individual commodities within the S&P GSCI index are updated every year in response to changes in global commodity production quantities and futures contract trading volumes.

Although still lower than in 2011 through 2014, crude oil prices rose for the second straight year after a crude oil production-cut agreement was executed among the Organization of Petroleum Exporting Countries (OPEC) and some non-OPEC countries, which partially constrained global crude oil production.

The agreement came into effect in January 2017 and will continue through the end of 2018. In addition to supply-side factors, strong economic growth in both developed and emerging markets has led to higher oil demand.