TOKYO -- Convenience store chain Lawson is expected to report its first drop in full-year operating profit in 15 years, taking a hit from the Japanese personnel shortage.

Lawson has seen costs balloon as it invests heavily in labor-saving technology. Operating profit apparently fell 10% to 66 billion yen ($617 million) for the year ended on Feb. 28, undershooting the company's forecast of 68.5 billion yen, a 7% drop.

Rising hourly pay for part-timers is weighing on franchise stores throughout the sector. Lawson's investments included a rollout of tablets at all stores to make ordering products and tracking employee attendance easier. In November, the company began introducing cash registers that automatically dispense the correct change to speed things up for inexperienced workers.

Lawson is also shelling out more in financial support for franchise stores, such as paying for disposal of unsold boxed lunches or certain utility fees. Costs associated with launching a banking unit this fall also increased.

Lawson opened 1,250 stores in fiscal 2017, including locations operated jointly with midsize partners Three F and Poplar, bringing its total tally at the end of February to about 14,000.

Spurred by openings of new stores, gross operating revenue -- the equivalent of sales -- likely climbed 4% to nearly 660 billion yen.

Existing-store sales were roughly flat. Food products, including prepared meals and dishes, sold well, as did rice balls and salads. Sales of health products such as low-sugar breads and vegetable drinks jumped, but sales of tickets for concerts and other events struggled.

Lawson has been prioritizing investment up through the present fiscal year in hopes of scoring an operating profit of 100 billion yen or more for the year ending February 2022.

Earnings are due out Wednesday. While the company aims to keep increasing sales by opening more stores, the persistent staff shortage means that labor-saving investments may lead to another year of declining operating profit.