Emerging markets have lost their luster for Big Pharma making drug firms ever more dependent on the United States for growth just as American anger over high medicine prices is building.

A few years ago, the developing world was seen as a savior as patent after patent expired across the United States and Europe, but a report in Reuters Health says that emerging market sales growth at the top drug firms slowed to less than two percent in the latest quarter.

Forecasts from independent experts IMS Health now suggest the United States will account for 55 percent of sales growth between 2016 and 2020, with emerging markets only contributing 30 percent.

The slowdown in China and other top emerging markets is being driven by a number of factors: government pressure on drug prices, slowing economies and in some cases significant currency devaluations.

But the end result is that prescriptions for Americans will fund an even greater slice of the $1 trillion-a-year pharmaceuticals industry.

Company executives insist markets from China to Colombia to Mexico to Myanmar are an important engine of long-term growth, given rising populations, increasing wealth, and the global march of diabetes, heart disease and cancer.

But the short-term picture is not pretty. Emerging market growth is the slowest since drug companies started breaking out such regional sales numbers about seven years ago, with GSK languishing at the bottom of the class.

GSK’s drug sales in China fell 14 percent in the three months to the end of June as the company continued to reshape its business following a damaging corruption scandal in 2013, leaving a question mark over whether it can return to growth this year as hoped.

Others are doing better in China, which is now the world’s second biggest drugs market behind the United States, but all are struggling with slowing sales growth, which slipped to its lowest rate since 2008 in July.

“Across the board, we are seeing emerging markets register lower growth in local currency and in many cases there have also been big currency devaluations,” said Murray Aitken, IMS Health senior vice president and executive director.

By comparison, the United States offers rich pickings at the moment thanks to hugely profitable new drugs for diseases such as cancer and hepatitis C.

Many companies’ sales in developing economies come from so-called branded generics, or off-patent medicines that command a premium to those made by local suppliers because the Western drugmaker’s name is a proxy for quality.

That business is now under threat as governments promote cheaper unbranded products as a route to universal healthcare.

One sign of the tougher times is the relative dearth of acquisitions in emerging markets by international players after a slew of multibillion-dollar deals between 2008 and 2011.