Why are Bund yields expected to rise?
Higher borrowing means Germany will issue more bonds, increasing supply. With more debt available, prices tend to fall, which pushes yields up, reflecting the market's demand for a higher return to hold the extra debt.
Could Bund yields actually fall on this news?
It's possible if investors interpret the tax shortfall as a sign of deep economic trouble, leading to a flight-to-quality where investors buy Bunds as a safe haven, driving prices up and yields down. However, the primary effect is supply-driven, favoring higher yields.
What timeframe should investors watch for this impact?
The market reaction could be immediate following the announcement, but the full impact on yields will unfold over the short-term as details of the borrowing plan are digested and as bonds are actually issued.