A comparison of the current housing market downturn with the slumps in the mid 1970s and early 1990s suggests prices could fall by a further 15% from October levels, with a recovery delayed until 2011 at the earliest.

On a quarterly average basis, the Halifax and Nationwide house price measures both peaked in the third quarter of 2007. By October, the Halifax index had fallen 16% versus 14% for the Nationwide.

The first chart below compares the inflation-adjusted decline in the Nationwide index with falls in the last three housing downturns – 1973-77, 1979-82 and 1989-95. The comparison is made in real terms because high inflation bore the burden of reducing housing valuations in the 1970s and early 1980s. The Nationwide index is used because the Halifax measure began only in 1983. The inflation adjustment is based on the retail prices index.

The decline in real prices since the third quarter of 2007 has closely matched the initial stages of the 1989-95 downturn. This was the most severe of the three, with a peak-to-trough fall in real prices of 37% over 26 quarters.

For comparison, real prices fell by 32% over 15 quarters in 1973-77 and 17% over 10 quarters in 1979-82.

The second chart reverts to nominal prices and shows illustrative scenarios assuming 1) inflation-adjusted house prices follow the same path as in 1989-95 or 1973-77 and 2) retail prices rise at a 2% annualised rate.

Interestingly, both scenarios suggest a bottom in nominal prices in the first half of 2011, at 15% and 13% respectively below the most recent – October – level. However, a repeat of 1989-95 would imply a further three years of stagnation, with a sustained recovery beginning only in 2014.

Could prices fall by even more than in the early 1990s? Based on the rental yield – a better measure than the house price to earnings ratio – housing overvaluation was less extreme in 2007 than 1989. Also, the early 1990s slump was exacerbated by sterling’s membership of the ERM, which constrained cuts in official interest rates.

However, these factors could be outweighed by the current mortgage famine, caused by banks' efforts to shrink their balance sheets, high funding costs and the rapid rundown of Northern Rock’s loan book. Cuts in official interest rates alone will have limited impact on mortgage credit supply.

Drastic action was warranted but there is a risk of exhausting interest rate ammunition too soon. The cut will have limited impact unless the financial system starts to function normally. The MPC is hoping to shock money and credit markets back to life but the Fed’s rate-slashing failed to avert a US credit crunch. UK policy-makers may need to consider additional steps to ensure the flow of credit to firms and households, such as TARP-style purchases of private sector debt and an expansion of the small firms loan guarantee scheme.

Headline money supply M4 numbers have been artificially boosted by a rerouting of interbank business through non-bank financial intermediaries, partly reflecting the operation of the special liquidity scheme. Unlike interbank lending, the deposits of these intermediaries are included in the M4 definition.

The Bank of England’s industrial analysis of bank deposits, published yesterday, permits a more accurate estimate of this effect. Specifically, an adjusted M4 measure was calculated excluding deposits held by five industrial categories within the financial sector – bank holding companies, mortgage and housing credit corporations, non-bank credit grantors, “other financial intermediaries” and “other activities auxiliary to financial intermediation”.

While headline M4 climbed 12.4% in the 12 months to September, the adjusted measure rose by just 2.9% – the lowest annual growth rate since 1999. In the latest three months adjusted M4 contracted at a 2.7% annualised rate.

While the headline M4 numbers are hugely inflated, the adjusted measure could in theory understate underlying broad money trends, to the extent that the non-bank intermediaries have created money-like liabilities. However, the bulk of their borrowing will have been from banks so any such effect should be small.

The collapse in money growth, when correctly measured, adds to arguments for a large cut in Bank rate tomorrow. Incorporating today’s services PMI results, my MPC-ometer now suggests a 55% chance of a full-point move and 45% of 75 basis points.

As previously reported, the liquidity ratio of private non-financial corporations – their M4 money holdings divided by bank borrowing – is at its lowest since 1991.

Bank of England data published today permit an analysis of liquidity ratios by industry. The low level of the aggregate ratio mainly reflects weakness in the real estate and construction industries.

“Normal” levels of the liquidity ratio vary by industry so it is more informative to monitor developments relative to a long-term average. The first two charts below show industry ratios relative to averages since 1998, when the Bank of England data began. In addition to construction and real estate, liquidity has deteriorated significantly in “legal, accountancy, consultancy and other business activities” – closely linked to property and financial markets.

By contrast, the liquidity ratio in manufacturing is above its post-1998 average and much higher than before the industrial recession in 2001.

The third chart shows the aggregate ratio for private non-financial corporations split between real estate and construction and other industries. The other industries ratio has declined sharply recently but has yet to fall beneath its level before the 2001 economic downturn.

The less dramatic liquidity deterioration outside real estate and construction may temper coming declines in business investment and employment. However, the industry skew is bad news for banks – real estate and construction loans account for 54% of their sterling lending to private non-financial corporations, having grown at an 18% annualised rate over the last five years.

The US stock market is at its lowest level relative to its long-term trend since 1984. This argues for a strategy of gradually increasing equity exposure - unless the trend is believed to be in the process of changing.

The chart below shows an index of inflation-adjusted equity returns since 1800 together with a trend line calculated on data up to 1999. The slope of the line implies an impressive real return of 7.1% per annum.

Interestingly, an almost identical line could have been estimated in 1950, based on data until then. The slope would again have equated to a real return of 7.1% pa. A simple extrapolation would have been a superb guide to real equity returns since 1950. Moreover, an investor could have beaten the market by increasing equity exposure when the return index moved below the line and cutting back when it rose above.

Consider someone updating the calculation in 2000. Such an investor would have concluded it was a poor time to own equities, even assuming the long-term trend would be sustained. The deviation between the return index and the trend line reached 82% in December 1999 - a level exceeded only in 1929.

The return index fell to touch the line at the bottom of the 2002-03 bear market, suggesting an investor buying equities at that point would earn the average 7.1% real return over the long term. The subsequent recovery restored a positive deviation, however.

The sharp fall of recent months has pushed the return index 48% below the line - the largest negative gap since 1984. While this appears to present a buying opportunity, deviations are often prolonged and can be more extreme than currently. This suggests adding gradually to equity holdings rather than moving straight to a maximum position.

Of course, the risk is that the trend is in the process of shifting lower from its historical 7.1% pa - such a change would not be clear in the data for several decades. However, its impressive stability despite major economic and political upheavals over the last 200 years offers reassurance.