Comparing the value of pounds in 1700 in Colonial America to the value of dollars today, is not an easy exercise.

There are several ways to do it, but all have their problems.

The relative value of things has changed so much between now and then, that it makes comparison difficult. Here is an example: From a probate inventory of the possessions of Valentine Bird, in 1680 in North Carolina, (http://www.learnnc.org/lp/editions/nchist-colonial/1635 http://www.learnnc.org/lp/editions/nchist-colonial/1646), we find that Bird owned three pair of fine Holland bed sheets, worth 50 shillings (2 pounds 10 shillings) a pair. His bedstead, was worth 8 shillings (20 shillings in a pound).

Today, this four poster bed from Pottery Barn, http://www.potterybarn.com/products/farmhouse-canopy-bed/?pkey=cbeds-headboards%7Cwood-beds-headboards%7C&&cbeds-headboards|wood-beds-headboards|, which might be similar to Mr. Bird’s bed, would cost $1600.

A good sheet set from Pottery Barn (including pillowcases, which Mr. Bird’s pair of sheets did not) would cost $200. http://www.potterybarn.com/products/pb-organic-400-thread-count-sheet-set/?pkey=csheet-sets&&csheet-sets

So, if we used the bed index to determine the value of pounds around 1700 to dollars today, we would calculate that 1 pound then was worth $4,000 today. That would make Reverend Parris’ 31 pounds worth $124,000.

If we used the sheet set index, then 1 pound then would be worth $80 today, and Reverend Parris’ 31 pounds would be worth $2,480.

There is a large difference between the two indexes. The relative value of bedsteads and sheet sets has changed massively since 1700. Sheets (like all textiles) were very expensive before the industrial revolution, when they were all spun and woven by hand, and, in the colonies, the finer sheets were all imported from Europe. Bedsteads, however, could be made locally by any competent carpenter, from readily available and cheap wood.

This website tries to make an indexed conversion from pounds in days of yore to dollars today: http://www.uwyo.edu/numimage/currency.htm

It thinks that a pound in 1700 would be worth about $189 in 2015. That would make Reverend Parris’ 31 pounds worth $5,859.

But, as you can see from the examples of the bedstead index and the sheet index, all such conversions of old money into today’s money are problematical estimations.

Colonial currency was a downright mess. The colonies were chronically short of specie because, with the exception of the sugar colonies, they were at a trade deficit with England/Britain. They shipped raw materials to England/Britain (and in fact New Englanders who had no cash crop made much of their money in the shipping business). The colonies then purchased back the more expensive manufactured goods. (Though it should be acknowledged that way more smuggling went on than the classic mercantilist understanding of the colonies presumes.)

How did the colonists function without liquid English/British currency?

(1) Use other forms of currency. The most widely used currency in the colonies was not an English/British coin but actually the Spanish eight reales piece. Massachusetts was the only colony to mint a significant amount of currency, which it did from 1652-82. That colony began to print its own currency in 1690 to pay troops fighting King William's War. These acted like government bonds. The government would issue a new tax equal to the amount of the bills it printed, thereby giving itself an advance. Colonists would receive a numbered bill that matched up to a stub the government kept, which could theoretically be returned, matched up, and paid out in silver (though this was rarely the case because the government also lacked specie). Instead, the best idea would be to pay taxes with these bills. The government offered you an extra 5% premium on the denomination of the bills for tax payments. This promise promoted public acceptance of the bills and allowed the government to collect some of the bills back in payment of taxes and then retire them.

With the shortage of silver though, it could be traded at a premium in the colonies. Therefore colonial currency values became decoupled from the English standard of the pound sterling. The Massachusetts General Court in fact legislated premiums on silver. In 1694, £133.66 in Massachusetts was equivalent to £100 pounds sterling. These rates varied for each colony based on their manipulations. That same year, £100 sterling was equal to £129.16 in New York and £135.86 in Pennsylvania. (From Purvis, Colonial America to 1763. table 4.195)

(2) Function on credit. Credit was integral to the functioning of the colonial economy. Statistics from the eighteenth century generally show more than 90% of transactions were made on credit. Credit in the colonial era functioned as a social bond, symbolizing friendship and creating obligations between people of various sorts. Promissory notes (IOUs) were circulated not only between individuals but within communities, further tying up obligations. David Flynn's article "The Duration of Book Credit in Colonial New England" suggests that debts were often held on the books for more than 15 months before they were repaid. Repayment could occur in cash, goods, or services.

Another way to wrap your head around colonial currency are rates for labor. In 1696, a field laborer made £7 (in local specie) over six months. A male servant in the 1690s made £12 (in local specie) for a year doing work like cutting and carting firewood, making fire, and tending cattle. A female servant would make £7 per year. (From Purvis, table 4.192) So £31 would be over twice what an unskilled male laborer would make in a year.