WASHINGTON — With little fanfare, China’s currency has appreciated significantly in the last year and a half, leading many economists to question whether the exchange rate is still the most important economic issue for the United States to press with China’s leaders.

The rise of the renminbi — up 12 percent since June 2010 on an inflation-adjusted basis and 40 percent since 2005 — has helped American companies by effectively reducing the cost of their products in China. In the last two years, American exports to China have risen sharply.

The renminbi remains undervalued, relative to all other currencies, by 5 to 20 percent, according to various estimates. But many business executives and economists say that other issues, like intellectual-property theft and barriers to entering Chinese markets, are now a bigger drag on the American economy.

In his Oval Office meeting on Tuesday with Xi Jinping, China’s vice president and likely next leader, President Obama discussed the currency as one of the trade practices that concerned the United States. That meeting — and tough public comments by Vice President Joseph R. Biden Jr. — continued a three-year campaign by the administration to convince Chinese leaders that a stronger currency is in their interest.