The 0.5% decline in GDP in the third quarter understates the scale of recent economic deterioration. A weighted average of monthly series for services and industrial output in July was slightly above its May / June average. The economy appears to have fallen off a cliff in August and September as the financial crisis escalated.

The GDP decline is consistent with an average path derived from the 1974-75, 1979-81 and 1990-91 recessions - see the chart below and the previous post for more details. The average path would involve GDP falling by 2-2.5% between the second quarters of 2008 and 2009, moving sideways over the following year and recovering by 2.5% in the year from the second quarter of 2010. Output would regain its recent peak level only in 2011.

This profile would imply an annual decline in GDP of 1.7% in 2009 followed by growth of just 0.4% in 2010 - significantly weaker than current consensus forecasts of -0.2% and 1.2% respectively (as reported by Consensus Economics Inc).

Incorporating the third-quarter fall into the MPC-ometer confirms the forecast of a cut in official rates of 75-100 basis points on 6 November. The model favours a full-point move if three-month LIBOR is still above 5.75% at the time of the meeting.

One way of "benchmarking" the current recession is to compare it with an average of the last three - 1974-75, 1979-81 and 1990-91. Based on the analysis below, an average recession path would involve GDP falling by 2-2.5% between Q2 2008 and Q2 2009, moving sideways over the following year and recovering by 2.5% in the year from Q2 2010. This would imply an annual decline in GDP of 1.7% in 2009 followed by growth of just 0.4% in 2010 - significantly weaker than current consensus forecasts of -0.2% and 1.2% respectively (as reported by Consensus Economics Inc).

Economists typically use quarterly GDP data to determine the timing and magnitude of recessions. However, GDP is sometimes distorted by strikes and other disruptions to normal economic activity. For example, GDP peaked in Q2 1973 and fell in each of the subsequent three quarters but much of this weakness reflected industrial action in the coal mining industry, culminating in the three-day week in Q1 1974. The analysis below uses a strike-adjusted measure of GDP, incorporating information on working days lost in industrial action, to calculate the depth of prior recessions. In addition, a judgement is made that the mid 1970s recession began in Q4 1974 rather than Q3 1973.

The first chart overlays the path of strike-adjusted GDP before, during and after the last three recessions on the current cycle. GDP is assumed to have peaked in Q2 2008 and the prior peaks are rebased and aligned to this starting point.

When the mid 1970s recession is dated to start in 1974 rather than 1973, it looks similar in magnitude and duration to the 1990-91 decline. However, the subsequent recovery was much swifter in the 1970s, probably because sterling's membership of the ERM constrained monetary easing in the later episode.

The peak-to-trough fall in GDP was significantly larger in 1979-81 - 6.2% versus 2.8% in 1974-75 and 2.5% in 1990-91. This dismal performance, however, was the mirror-image of much stronger growth in the year before the GDP peak - 5.3% against 0.3% and 1.6% respectively. Relative to its value four quarters before the peak, GDP troughed at similar levels in 1981 and 1991, with a slightly larger decline in 1975.

This last point suggests calculating a benchmark future path by averaging the performance of GDP relative to its level four quarters before the peak across the three cycles, rather than relative to the peak itself. The result is shown in the second chart and is the basis for the description of an average recession path given earlier.

As argued in previous posts, the current recession could be less severe than the last three, because the preceding boom was smaller, interest rates have risen by less and the exchange rate has been unusually weak. Such mitigating factors, however, will be overridden if current financial paralysis persists. Detailed monetary statistics for September to be released next Wednesday will provide further information on the damage to economic prospects from the financial freeze.

A week before the October MPC meeting the MPC-ometer forecast a quarter-point rate cut - at odds with the majority view of no change in a Reuters poll. By the time of the decision the projection had changed to half a point, allowing for the "shock" from escalating financial turmoil - see here.

Minutes of the special MPC meeting on 8 October confirm that recent financial events have resulted in a fundamental shift in the Committee's thinking. The focus now is on averting the "tail risk" of a severe recession and significant inflation undershoot. In terms of the MPC-ometer, this shift can be captured by "switching on" the shock variable that played a key role in explaining the MPC's behaviour after the 9/11 terrorist attacks.

The model's forecast will also depend importantly on Friday's third-quarter GDP report as well as consumer and business surveys to be released around month-end. Assuming a quarterly GDP decline of 0.2% and unchanged survey responses, the -ometer suggests a three-quarter-point cut at the next meeting on 5/ 6 November.

As discussed in previous posts, an alternative version of the model assumes the MPC targets interbank interest rates rather than Bank rate. This projects a full-point Bank rate cut in November if three-month LIBOR is above 5.75% at the time of the meeting (fixed at 6.04% today).

Both versions suggest the MPC will go on hold in December and January if the November forecasts prove correct.

For comparison, the overnight indexed swap curve currently discounts a 62 basis point cut by 6 November with further falls of 14 bp in December and 17 bp in January.

Federal Reserve Bank credit - the Fed's lending to banks, dealers, other central banks and AIG plus its holdings of securities - has soared by $850 billion, or over 90%, since 11 September, just before Lehman's failure. Importantly, the Fed has chosen not to sterilise fully the impact of this expansion on banks' reserves - their deposits held at the Fed. Reserves and currency in circulation constitute the monetary base. The average level of the base in the fortnight to 8 October was 17% higher than four weeks earlier.

Real monetary base expansion tends to lead economic activity so the recent pick-up could suggest improving growth prospects - see first chart. Historically, however, major swings in base money have been driven by the currency component rather than bank reserves. The hope is that banks holding excess cash in their accounts at the Fed will be more willing to lend to other banks and the wider economy but many commentators believe the Fed is "pushing on a string".

The Fed is copying the Bank of Japan's 2001 policy of "quantitative easing", which involved the central bank buying government bonds in order to flood the banking system with liquidity. Real monetary base growth peaked at an annual 38% - see second chart. Commentators were similarly sceptical of any impact on financial behaviour or economic activity but growth recovered in 2002, while the rate of contraction of bank lending slowed, although these improvements may have reflected other factors.

The UK’s bank recapitalisation plan is unlikely to lead to a near-term revival in credit and money growth. Indeed, the initial impact of the scheme will be to reduce the broad money supply M4, implying a need for offsetting monetary easing measures, including interest rate cuts.

The negative M4 impact arises because a portion of the additional gilts and Treasury bills being issued to finance the recapitalisation will be bought by the non-bank private sector, implying a transfer of money out of bank deposits included in M4 into government coffers. If the entire £37 billion were raised from private non-banks – admittedly unlikely – M4 would be cut by 2.0%, before allowing for second-round effects.

This negative impact would be offset if banks used the funds injected by the government to increase their lending. However, the aim of the scheme is to raise capital ratios to a new higher level that banks will be required to maintain over the medium term, rather than provide them with “excess” capital to support additional balance sheet expansion. In other words, any increase in lending may depend on further capital-raising – arguably made more difficult by the stringent terms of the “rescue”.

The negative impact on M4 would be avoided if the government were to fund the recapitalisation by borrowing from the Bank of England but this would be at odds with current institutional arrangements and EU Treaty obligations discouraging central bank lending to governments.

The Debt Management Office plans to increase sales of gilts and Treasury bills by £30 billion and £7 billion respectively in 2008-09. There is a strong case for boosting the amount to be raised from Treasury bills, since these are more likely to be purchased by banks themselves, thereby avoiding a transfer of funds out of M4 deposits.

Headline M4 expansion rose to an annual 12.2% in September but continues to be badly distorted by the financial crisis. Underlying growth – excluding the contribution of non-bank financial intermediaries – fell from 13.6% to 6.5% between June 2007 and June 2008 and is likely to have slipped further more recently (September data will be available in early November). Underlying M4 probably needs to expand by 6-8% per annum to keep inflation on track to meet the 2% inflation target over the medium term. (This assumes trend GDP growth of about 2.5% and a decline in M4 velocity of 2-3% pa, in line with the average over 1992-2004, when inflation was close to 2%.)