Is the expression level of miRNA precursors lower compared to that of mature miRNAs?
FAQ ID -2807

In general, precursor miRNA (pre-miRNA) levels are lower than those of mature miRNAs. However this is not always the case. Sometimes the levels of both mature and pre-miRNA may be similar, or pre-miRNA levels may be higher. For this reason, researchers often want to quantify pre-miRNA as well as mature miRNA.  QIAGEN offers miScript precursor miRNA assays as well as mature assays for many miRNAs.