The percentage of technology and engineering companies founded by immigrants has declined over the past seven years, according to a new nationwide study by the not-for-profit Kauffman Foundation. But the drop has been particularly pronounced in Silicon Valley, long one of the country's most vibrant entrepreneurial hotspots.

Since 2005, the share of businesses led by immigrants dipped to 24.3% from 25.3%, the study reports. In Silicon Valley, the percentage of companies led by immigrants decreased to 43.9% from 52.4%. 

The Foundation polled a randomly selected group of 1,882 technology and engineering companies started within the past six years. Of those, only 458 said they had at least one foriegn-born founder. This is the first immigrant-focused study from Kauffman since 2007, when the foundation polled immigrant-led companies founded between 1995 and 2005. 

Michael Wildes, a New York City-based immigration lawyer, said in a statement that the decline is a result of the US' tight immigration policies. Specifically, he said high Visa costs, decreased Visa availability, and sluggish reforms from the DREAM Act and the STEM Jobs Act were limiting entrepreneurs' ability to come to the U.S. 

"More and more talent, especially in critical sectors like the STEM fields, is staying overseas," Wildes said in a statement. "They want to come here, we just aren’t letting them."

But the study did find one notable upswing in entrepreneurship among Indian immigrants. Of the foreign-born founders polled in the study, 33.2% of them hailed from India--a seven percent increase from 2007.