Data science ranks among the skills with the most demand growth from online staffing users in the U.S., according to a new report by Elance-oDesk. Other skills with growing demand include Internet security, content marketing, Android app development and 3D modeling.

Skills with decreasing demand in the U.S. include Facebook development, SEM, infographics, AJAX programming and Joomla! development.

Elance-oDesk was formed through the merger of two of the largest online staffing firms — Elance and oDesk — which was announced late last year.

The company also reported $231 million in online work spend from the U.S. between January and May, an increase of 29 percent over the same period last year. The online staffing firm estimates total U.S. spend will reach approximately $500 million for full-year 2014 with total global spend reaching $930 million.

In the U.S., writing & translation represented 30 percent of freelancer earnings; it was followed by technology at 29 percent. The greatest increase in spend was in the manufacturing & engineering category, which increased 88 percent despite representing only 2 percent of total spend.

CEO Fabio Rosati said 25 percent of jobs are filled within 24 hours and a majority of jobs are filled within three days.

“If you are someone looking for work, it is entirely possible for the first time ever in humanity to get hired within hours by someone you don’t know,” Rosati said.