The news just keeps getting better for restaurants. Really.

The National Restaurant Association's Restaurant Performance Index for March indicates that the economic health of U.S. eateries improved sequentially, largely because of improvements in same-store sales and traffic. The index clocked in at 101.0 in March, up 0.3 points from February. A figure over 100 indicates expansion in the restaurant sector.

Better still, it was the sixth time in seven months that the index came in above 100, indicating a more sustained level of expansion. A notable exemplar has been McDonald's (NYSE: MCD), whose U.S. same-store sales came in at 2.7% and 3.1% in February and January, respectively. For the first quarter ending in March, the company noted U.S. comps of 2.9%.

Other restaurant heavyweights have seen similarly good performances over the last few months. Chipotle (NYSE: CMG) reported comps as fat as its burritos, at 12.4% for the first quarter. Panera Bread (Nasdaq: PNRA) revealed a 3.3% comps gain in its quarter and a more than 5% boost in April (as of its first-quarter report). Sonic (Nasdaq: SONC) pre-released same-store sales figures for March and April, which came in between 4% and 6% -- a notable improvement for the struggling drive-in.

Results at other chains were more spotty. The first quarter wasn't quite so pink at Yum! Brands (NYSE: YUM), at least in the U.S., which saw a 1% decline in same-store sales. The real story at Yum! concerns its massive growth in China, where comps soared 13%.  Brinker International (NYSE: EAT) saw systemwide comps off 0.2% in its latest quarter.

While the restaurant index did indicate improving sales in the months ahead, it also noted that restaurants were less sanguine about the overall direction of the economy, with only 32% anticipating improved conditions in the next half-year.

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