Retailers ranked in the Internet Retailer 2016 Europe 500 grew web sales to 145.01 billion euros ($161.60 billion) last year, up by 16.8% from 124.16 billion euros ($138.36 billion) in 2014. That rate outpaced overall retail sales growth in Europe, which Ecommerce Europe placed at 13.3%.

E-commerce sales grew in all of Europe in 2015 to 455.30 billion euros ($516.39 billion) from 401.85 billion euros ($455.91 billion), Ecommerce Europe says in a new report. The top performers in European e-commerce—those companies ranked in the 2016 Europe 500—accounted for 31.8% of those online sales.

Europe still leads the United States in total e-commerce sales. In 2015 U.S. web shoppers spent $341.73 billion, by the U.S. Commerce Department’s measurements, up by 14.6% from 2014. Europe is second only in worldwide web sales to China, where 2015 online sales reached $589.61 billion, up by 33.3% from 2014, according to the National Bureau of Statistics in China.

Overall e-commerce sales growth in Europe came from 296 million consumers—43% of the population over age 15—who shopped online. Of 685 million consumers in Europe, 516 million (75%) used the internet last year, according to Ecommerce Europe, a trade organization comprising more than 25,000 companies that sell products online in Europe.

Countries in Western Europe accounted for 55.5% of all European e-commerce sales in 2015 as web sales in Belgium, France, Ireland, Luxembourg, the Netherlands and the United Kingdom reached 252.86 billion euros ($282.00 billion). That’s up by 12.9% from 2014, Ecommerce Europe reports. Those Western European countries led the way in online sales last year, Ecommerce Europe says, booking more than half of all European e-commerce sales despite having only 24% of the population. That’s because 75% of the population over age 15 (101 million) shops online, compared with the overall rate in Europe of 43%, Ecommerce Europe says. The average web shopper in the six countries that the report categorizes as in Western Europe spent 2,492 euros ($2,779) last year, 61.8% more than the overall European consumer’s average spend of 1,540 euros ($1,717).

The U.K. led Western Europe in 2015 e-commerce sales with 157.15 billion euros ($175.26 billion) in web sales, followed by France at 64.90 billion euros ($72.38 billion) and the Netherlands with 16.07 billion euros ($17.92 billion). The report did not break out growth rate by individual countries.

Nearly all growth in European retail came from e-commerce in 2015, Ecommerce Europe says, as overall retail sales increased only by 1%. While the e-commerce sector “is booming, the full potential of the European e-commerce market has not yet been reached. Today, 57% of European internet users shop online, but only 16% of small to medium-sized businesses sell online, and less than half of those sell online across borders (7.5%).”

Southern European countries—Spain, Italy, Turkey, Greece, Portugal, Croatia, Cypress and Malta—had the highest e-commerce growth rate last year at 17.1%, reaching 50.9 billion euros ($57.75 billion). Spain led the region with 18.2 billion euros ($20.65 billion) in online sales, followed by Italy at 16.60 billion euros ($18.83 billion). 30% of 172 million consumers over age 15 shopped online in Southern Europe last year and 66% of consumers used the internet.

While growth in some more mature e-commerce markets, such as the U.K., Germany and France, is expected to level off in the next few years, online sales in Southern and Eastern European countries will grow, Ecommerce Europe says. Key growth factors include increasing confidence in online shopping, higher disposable incomes and expansion of mobile commerce conducted on smartphones and tablets, Ecommerce Europe says in its report, which encompasses 47 countries including 28 members of the European Union. The report projects 2016 online sales will reach 510.00 billion euros ($578.49 billion), up 12.0% from 2015.

Among the other three European e-commerce regions:

• Central European countries—Germany, Switzerland, Poland, Austria, Czech Republic, Hungary, Slovakia and Slovenia—grew web sales 14.2% in 2015, to 89.50 billion euros ($101.49 billion) from 78.37 billion euros ($88.87 billion). Germany was the online sales leader at 59.70 billion euros ($67.70 billion) followed by Switzerland at 8.53 billion euros ($9.67 billion).

• Northern European countries, including Denmark, Sweden, Norway, Finland, Lithuania, Iceland, Latvia and Estonia, grew online sales 10.9% in 2015 to 37.60 billion euros ($42.64 billion) from 33.90 billion euros ($38.45 billion). Denmark’s 2015 online sales were 11.65 billion euros ($13.21 billion), tops in the region. Sweden followed at 9.67 billion euros ($10.97 billion).

• Eastern European countries—Russia, Romania, Ukraine, Bulgaria and eight other smaller nations—booked a 9.1% increase in online sales, to 24.50 billion euros ($27.79 billion) from 22.46 billion euros ($25.47 billion). Russia’s e-commerce sales were 20.54 billion euros ($23.29 billion) followed by Romania at 1.40 billion euros ($1.59 billion).

For more information on Internet Retailer’s new report on European e-commerce and the new Internet Retailer 2016 Europe 500, available in database format, click here.