"has decreased below" is a perfectly grammatical and usable part of a sentence in written English.
You can use it when you want to indicate that something has been reduced to a lower amount or level. For example: "The humidity in the room has decreased below 50%."
Given these cuts and the volatility in the credit markets, lender returns on student loans have decreased below an acceptable level, forcing lenders to decline to make certain loans.
By August, soil EC had decreased below 4 mS cm− 1 at the 0 15 cm depth.
In fact, Ludwig et al. [17] found that the antibody levels of 50% of the patients with HUS had decreased below the respective cut-off levels at 3 months after the onset of diarrhea.
By day 7, however, mean LH had decreased below baseline.
Influenza outbreak dynamics are relatively poorly understood, and the proportion of children who were susceptible to infection might have decreased below the number required to sustain transmission at approximately the same time schools were closed.
During enrichment phases 1-5 no H2 was produced in any of the cultures, while in enrichment phases 6 to 9 low levels of H2 were detected in B-C and B-D enrichments during the first few days, but usually by day 5 the H2 level had decreased below detection limit (results not shown).
The campus is one of Cal State's most diverse, but even there African American enrollment has decreased to below 18% from nearly 30% in 2009.
Recent data from the Chinese Network for Bacterial-resistance Surveillance demonstrated that the susceptibility of A. baumannii to carbapenems has decreased to below 50%, and almost 17% of these isolates are resistant to all antimicrobial agents that are routinely used in clinical practice [ 2].
As mentioned before, it is common opinion that HBV-vaccinated subjects with an anti-HBs titer that has decreased to below 10 UI/L or that have become anti-HBs negative are still considered protected against HBV infection, since the immunological memory to HBsAg may persist even in these cases and ensure a rapid rise of protective antibodies in the case of an HBV assault [ 13, 18, 28].
