Proponents of this view point to difficulties in filling technical positions (particularly those that require American citizenship due to security restrictions), declining enrollment in science and engineering programs, looming waves of retirement among baby boomer scientists, and the fact that the entire annual supply of H1-B visas (for highly skilled immigrants) is used on the first day they become available.
What is not clear? The structure? The words, like "proponents" or "baby boomer" or "looming"? The extra-linguistic meanings, like "What constitutes a security restriction?", or "How do H1-B visas work?"
Proponents of this view
point to:
1. difficulties in filling ... positions ... 2. declining enrollment ... 3. looming waves of retirement ... 4. the