Method and Definitions

Definition of Relationship
A relationship in this study is any intimate or romantic liaison lasting from one night to 70+ years. Included were any relationships between public figures whose biographical details (dates and places of birth) and pertinent information about their relationship (where and when they met and/or married and if they split up) could be researched via online or offline biographical sources. In the original 2005 experiment any historical relationship that met the criteria for inclusion (described below) was included, but this was limited in the 2019 replication experiment to those where both partners were born after 1800CE. This is because researching Old System/New System (OS/NS) dates can create a number of research overheads. 

Data Collection
The idea for this study can be traced to June 1997. The first set of 1,300 public record relationships was collected from various online and offline biographical sources and researched between the years 2000 and 2004. Manual calculation of this dataset was completed in 2005. 
The method of data gathering was either thematic (looking at and including all public relationships in a specific group i.e. silent movie actors, French cinema stars, the Bloomsbury Set, the Beatles, US Presidents etc.)  or opportunistic (looking at famous individuals and then all of the relationships connected to that person: e.g.,  Frank Sinatra and all his partners -> including Ava Gardner and all her partners -> including Artie Shaw and all his partners -> including Lana Turner and all of her partners, etc. etc

Here’s a look at how I describe part of this process:
An online source stated that Artie Shaw was to married Lana Turner and had dated Ava Gardner, more biographical research showed that Ava Gardner had married Frank Sinatra who had also dated Lana Turner who in turn had dated Fernando Lamas who had dated Esther Williams and who was also married to Arlene Dahl who had in turn been married to Lex Barker who  had also married Lana and the researcher is back at the beginning because the fact that Lana married Artie Shaw has already been recorded, but a new line of enquiry (or arm of the web) begins here because Artie Shaw also married Evelyn Keyes who dated David Niven, Mike Todd and so it goes on. It would then be necessary to follow all of the branches of this web relating to Niven, Sinatra, Gardner, Arlene Dahl, Lex Barker, Lamas, Williams and whoever else was included until the researcher arrived at a non-public relationship or someone for whom accurate data was unavailable (Mike Todd for instance was excluded because he had a number of different birth certificates). A new line of enquiry was then begun through further research.

Some of these ended up being single relationships, but many spread into very wide ‘webs’ involving multiple degrees of separation). It was important to always dig to see if there were more public relationships with valid data for every individual in the study, in this respect the data collection method employed is virtually the same as Criminal Groups Analysis sometimes known as Criminal Network Analysis and Crime Link Analysis,  but in this case applied to the intimate relationships of famous people rather than organised crime groups. This resulted in some dead-ends which opened up later, for example, it was not possible to find birth details of Shirley MacLaine’s husband Steve Parker during the original study, but 17 years later this information was discovered, so this relationship is included in the replication study.

We should be aware that this study is based upon historical data, and the data is therefore open to improvement. These ongoing improvements have, so far, increased the level of significance of the claimed effects.

From 2004 to 2018, the second set of 1,300 public relationships was collected and researched. As noted previously, any with a pre-1800CE birthdate or any that contained any person who is not a public figure with a researchable history (e.g., if their place of birth was unavailable) were excluded. Times of birth are included where available, the source being (in 2005) the Astrodatabank 3.0 application and (in 2019) the Astrodatabank web site. The rationale behind this is that data without a time of birth is commonplace and usually accurate (the vast majority of UK birth certificates do not include time), whereas data with no firm place of birth is rare, and the source is invariably less trustworthy.

Criteria for Inclusion
These relationship webs and themes were followed, and new public or historical couples incorporated according to the following rules:
1.    Both dates and places of birth are available and not in dispute. 
2.    The relationship is reliable (it really was/is an intimate or romantic relationship) and a start date or marriage date is available and not in dispute 
3.    There was no arrangement by a third party or evident coercion involved in the forming of the relationship (arranged 
marriages were not considered).

Public relationship in this context requires that all the data about the relationship is available, including both dates of birth and details of the marriage-date or the start date of the relationship. At least one person (and usually both) in each relationship has an online biographical record in Wikipedia and/or a publicly available biography at Astrodatabank.
By looking at large numbers of relationships, aspects were counted to see if they occurred more or less often in intimate relationship scenarios. The start-date (if available) or marriage date (if a reliable start-date was not available) was used as the point-in-time for secondary progressed planetary positions.  Any relationship that did not end in marriage had to have a start-date (which is usually just the year the relationship began) to be included.

Orbs Used
In order to see developing progressed aspects, to allow for noon-births and to eliminate the noise created by wide orbs, 2 degrees and 1 minute orbs were used at the outset (this was originally a manual study and uses noon-births in order to allow for a more substantial population). The 2° 01” (as opposed to a 2 degree orb (Ebertin 1956)) was chosen because of the need to manually identify the aspects by visual inspection. This involves doing a mental calculation based on the distance between two bodies in the zodiac using data from an ephemeris (this is something that experienced astrologers can do quite quickly). It is far easier and quicker to calculate 00TAU00 to 02SCO00 (which is two degrees and 1 minute) as an opposition, than limit it to 00TAU00 – 01SCO59 (which is two degrees). Lack of certainty as to how the minutes of arc were calculated and rounded in the ephemeris was also a factor, so it was simpler and easier to consistently add the extra minute of arc.

In total, 1,790 marriages were included and 810 love affairs (1790 marriages + 810 love affairs = 2600 = 1300 x 2).  It was noted by a reviewer that marriage dates and relationship start dates are different and may be associated with, or reflect, different conditions and astrological phenomena. This view does not fully take into account the fact that all astrological aspects including progressed synastry aspects involving Venus exist in continua which form and fade, and the orb used in this study attempts to capture the phenomena of the synastry aspect as it occurs over time. Marriages begin as meetings which become relationships, but the marriage date, which is conveniently available, is often the date recorded as the beginning of the relationship in source media.  Using a two-degree orb, we capture about 4.5 years of the continuum; using a 3 degree orb, about 6 years, meaning that we often capture important synastry aspects if we use either the relationship start date or the marriage date.
The mean age difference between the couples in the real data is 2,952.544 days (8 years). This is a high average.  The wide difference in ages in many of the mid-20th Century couples may be associated with the power (of both men and women to choose partners rather than accept what is available in a small-pool) and ambition (some relationships enabled individuals to achieve more professionally). Other contributory factors, which may have affected a smaller proportion of the population, include the reduced availability of young men post-WW1 and post WW2, although in these celebrity relationships, this may be less relevant than in wider society.