Sales of digital manga in 2017 surpassed their printed versions for the first time, an industry research institute said Monday, highlighting a shift in reader preferences.

According to a survey by the Research Institute for Publications, sales of digital manga last year are estimated to have risen 17.2 percent from a year earlier to ¥171.1 billion ($1.6 billion), while sales of physical manga fell roughly 14.4 percent to ¥166.6 billion.

According to the research group All Japan Magazine and Book Publisher's and Editor's Association, consumers are increasingly drawn to viewing online content partly due to discount campaigns for digital works that were past hits.

The concluding of some popular series and a lack of new blockbusters are believed to be behind the slump in physical sales, said the Tokyo-based research body.

Combined sales were almost unchanged in 2017, declining 0.9 percent from a year earlier.