According to a report in Professional Jeweller, hallmarking of gold jewelry overall has declined 11.8% year-over-year. Higher gold prices were blamed, even though the steepest decline in hallmarking was for 9 karat jewelry.
Presumably, the steep decline in 9 karat pieces was due to them being sold to a more price-sensitive clientele. That group seems to have little crossover with the other categories. The drop in demand for 9-karat category was not compensated for by an increase from people who would otherwise have bought 14 karat.