Reflecting increased optimism among operators, the restaurant industry’s monthly report of business conditions rose to its highest level in two years.

The National Restaurant Association’s Restaurant Performance Index (RPI) rose to 102.1 in May, up 0.4% over April and the strongest reading since March 2012, according to a news release from the association.

The index stood above 100 for the 15th consecutive month, according to the release. Any score above 100 indicates the restaurant industry is expanding, according to the release.

“Positive sales results fueled the May increase in the RPI, as nearly two-thirds of restaurant operators said their same-store sales rose above year-ago levels,” Hudson Riehle, senior vice president of the Research and Knowledge Group for the association said in the release. “In addition, restaurant operators are increasingly optimistic about continued sales gains in the months ahead, a sentiment that is also showing up in their capital expenditure plans.”

May marked the third straight month that most restaurant operators reported higher same-unit sales, according to the release. Sixty five percent of operators reported a same-store sales growth between May 2103 and May 214, up from 51% in April and the highest level since March 2012, according to the release.

Traffic at restaurants was reported up by 47% of operators in May compared with year-ago levels, according to the release. That is up from 44% in April who reported a traffic gains compared with April 2013.

The May survey reported half of all restaurant operators expect to have higher sales in six months, up from 46% who felt that way in April. Only 8% of operators expected lower sales in six months, down from 11% in April.

Still the release said restaurant operators aren’t sure about the country’s economic direction. The survey found that 28% of restaurant operators said they expect economic conditions to improve in six months, compared with 15% who expect the economy to shrink and 57% who expect conditions to remain about the same.