Reading the chart
One continuous SONIA line, past meets implied future
The dark navy line is a single continuous view of SONIA across time. To the
right of "Today" (the dashed vertical line) it shows the
implied 3-month forward SONIA rate for a 3M period starting at each
calendar date, derived from today's Term SONIA OIS swap curve — i.e. the
rate at which a forward-starting deposit would price using current swap
discount factors. To the left of "Today", when historical overlays
are active, the line extends backwards with realised daily SONIA fixings,
so the past and the implied future read as one path.
Other elements on the chart
- Faded dotted line — implied path computed from today's first intraday snapshot ("today's open"). The gap to the latest line is today's intraday move along the curve.
- Orange step line — implied Bank of England Bank Rate, computed by averaging the implied SONIA between consecutive scheduled MPC meetings and rounding to the nearest 25bps.
- Green bars (right axis) — change vs yesterday's close at each tenor, in basis points.
- Vertical dashed line — today's date marker, separating realised history from implied future.
Comparing to history
"Compare to" overlays
Buttons overlay an end-of-day snapshot from 1 week up to 1 year ago.
Multiple periods can be active at once, shown in graduated blue shades
(older = lighter). Each historical curve is plotted date-aligned: a
given calendar period (say Apr-2027) sits at the same x-position on every
line, so you can read directly how the market's view of that period has
revised over time.
1-year range band
The 1yr range button shades a faint grey envelope showing, at each
calendar date, the min and max implied 3M forward seen across all daily
EOD curves that priced that date — with a dashed median line through it.
Forward of today the band uses every available historical curve; backward
of today it uses only curves older than the date in question, and it clips
to the earliest active overlay so the past portion only shows where you
have context for it.
How to read it: if today's path sits at the top of the envelope at
a given calendar date, the market is pricing that forward richly versus
the last year of history; bottom of the envelope, cheaply.
Interactions
- Click any point or green bar — pins a popover with the implied rate and detailed deltas (vs prior close, vs today's open).
- Toggle multiple "Compare to" buttons — overlay several historical curves at once.
- Click "Clear" — removes all overlays and the range band in one go.